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Microstructure and Mechanical Properties Relationship for Metallic Materials
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Microstructure and Mechanical Properties Relationship for Metallic Materials

A special issue of Materials (ISSN 1996-1944). This special issue belongs to the section "Metals and Alloys".

Deadline for manuscript submissions: closed (10 September 2023) | Viewed by 50803

Special Issue Editor

Prof. Dr. Jan Džugan

E-Mail Website
Guest Editor
COMTES FHT a.s., Dobrany, Czech Republic
Interests: thermomechnical processing; SPD processing; additive manufacturing; local properties assessment; functionaly graded materials; MSNAT
Special Issues, Collections and Topics in MDPI journals

Special Issue Information

Dear Colleagues,

The application potential of engineering materials is related to their properties for the considered use. For metals, the potential exists to improve or tailor properties for specific and especially high-end applications through the processes affecting the microstructure evolution. These processes include heat treatment, thermomechanical treatment, severe plastic deformations processes, or basically processes of casting, welding, or recently additive manufacturing, which can play a significant role in the creation of the desired properties of traditional metallic materials. Currently available processes provide not only homogeneous materials but also yielding heterogeneous and functionally graded materials, such as additive manufacturing, laser processing, processing with inductive treatment. All considered processes produce a specific microstructure that is mirrored in distinct mechanical, physical, or thermo-physical properties that are required for engineering applications.

This Special Issue is focused on papers considering the relationships between microstructure and related properties for the application of advanced metallic materials. This Special Issue will collect quality papers providing a sound base in the field for present and future scientists dealing with the enhancement of metallic materials properties for specific high-end applications.

Prof. Dr. Jan Džugan
Guest Editor

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Submitted manuscripts should not have been published previously, nor be under consideration for publication elsewhere (except conference proceedings papers). All manuscripts are thoroughly refereed through a single-blind peer-review process. A guide for authors and other relevant information for submission of manuscripts is available on the Instructions for Authors page. Materials is an international peer-reviewed open access semimonthly journal published by MDPI.

Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) for publication in this open access journal is 2600 CHF (Swiss Francs). Submitted papers should be well formatted and use good English. Authors may use MDPI's English editing service prior to publication or during author revisions.

Keywords

  • microstructure
  • mechanical properties
  • thermo-physical properties
  • fracture
  • plasticity
  • metals
  • anisotropy
  • functionally graded materials
  • SPD
  • additive manufacturing

Published Papers (28 papers)

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Research

17 pages, 8949 KiB  
Article
Kinetics of Nickel Diffusion into Austenitic Stainless Steels AISI 304 and 316L and Calculation of Diffusion Coefficients
by Šárka Bukovská, Jaromír Moravec and Martin Švec
Materials 2023, 16(20), 6783; https://0-doi-org.brum.beds.ac.uk/10.3390/ma16206783 - 20 Oct 2023
Cited by 2 | Viewed by 795
Abstract
Diffusion bonding has many advantages, but it also has its specifics. When creating heterogeneous joints, problems arise with the creation of intermetallic phases. For this reason, an interlayer is needed to prevent the creation of these unfavorable phases. It is important to ensure [...] Read more.
Diffusion bonding has many advantages, but it also has its specifics. When creating heterogeneous joints, problems arise with the creation of intermetallic phases. For this reason, an interlayer is needed to prevent the creation of these unfavorable phases. It is important to ensure that the interlayer is of sufficient thickness to prevent the elements from diffusing through the entire interlayer and the intermetallic phases from being formed again. Conversely, too thick an interlayer causes an increase in the heterogeneity of the bond properties. The creation of the initial diffusion bonds in a heterogeneous diffusion joint of AISI 304 and AISI 316L steel with a 0.2 mm thick nickel interlayer was made in a Gleeble 3500. The experiments to determine the diffusion kinetics were carried out in a vacuum furnace, with subsequent evaluation by EDX (Energy Dispersive X-ray Spectroscopy) analysis. Subsequently, the diffusion coefficients of nickel into both steels were determined, and generalized equations were formulated to calculate the diffusion coefficients for temperatures in the range of 950 to 1150 °C and holding times in the range of 3600 to 18,000 s. Equations are also given to determine the width of the diffused zone between each steel and the Ni interlayer. Full article
(This article belongs to the Special Issue Microstructure and Mechanical Properties Relationship for Metallic Materials)
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14 pages, 6977 KiB  
Article
Kinetics of Austenite Decomposition in 54SiCr6 Steel during Continuous Slow Cooling Conditions
by Aleksandr Gokhman, Petr Motyčka, Pavel Salvetr, Zbyšek Nový, Jakub Kotous, Arkadii Briukhanov and Ján Džugan
Materials 2023, 16(13), 4619; https://0-doi-org.brum.beds.ac.uk/10.3390/ma16134619 - 27 Jun 2023
Viewed by 706
Abstract
In this study, dilatometry and metallography were used to investigate the effect of silicon and copper alloying on the decomposition kinetics of 54SiCr6 steel during continuous slow cooling. It is different from the published literature for using the approach of the local activation [...] Read more.
In this study, dilatometry and metallography were used to investigate the effect of silicon and copper alloying on the decomposition kinetics of 54SiCr6 steel during continuous slow cooling. It is different from the published literature for using the approach of the local activation energy of the austenite decomposition Ef and the local Avrami exponent n of the volume fraction of the transformed phase f to study the kinetics of austenite-pearlitic transformation in cooled 54SiCr steel at slow cooling rates. The Johnson–Mehl–Avrami equation was used to determine the dependence of the local activation energy for austenite decomposition Ef and the local Avrami exponent n on the volume fraction of the transformed phase f. The mechanism of the austenite decomposition was analysed based on the calculated values of n. Both the local and average activation energies were used to evaluate the alloying effect, and the results were compared with those obtained from other methods. The type of microstructure formed as a result of cooling at rates of 0.5 K/s, 0.3 K/s, 0.1 K/s and 0.05 K/s was determined. The effects of changes in the cooling rate and the content of silicon (1.5–2.5 wt.%) and copper (0.12–1.47 wt.%) on the dimension of nucleation and growth kinetics of the transformed phase were studied. It was revealed that the pearlite microstructure was formed predominantly in 54SiCr6 steel as a result of continuous cooling at slow cooling rates. It was also found that alloying this steel with copper led to a significant decrease in the value of Ef, as well as to a change in the mechanism of the kinetics of the austenite-pearlite transformation, which was realised in predominantly two- and three-dimensional nucleation and growth at a constant nucleation rate. At the same time, alloying this steel with silicon led only to a slight change in Ef. The results of the study of 54SiCr steel presented the dependence of the activation energy of transformation and the local Avrami exponent on the volume fraction of the transformed phase at a given cooling rate at different copper and silicon contents. In addition, the study provides insight into the mechanism of kinetics in cooled 54SiCr steel as a function of the cooling rate. Full article
(This article belongs to the Special Issue Microstructure and Mechanical Properties Relationship for Metallic Materials)
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12 pages, 6525 KiB  
Communication
Aspects of Austenitization for the Bearing Steel Induction Quenching Design
by Daniela Nachazelova, Jaromir Dlouhy, Petr Motycka and Jakub Kotous
Materials 2023, 16(9), 3523; https://0-doi-org.brum.beds.ac.uk/10.3390/ma16093523 - 04 May 2023
Cited by 2 | Viewed by 967
Abstract
The dissolution of carbides during the heating to the quenching temperature has a significant effect on the martensite oversaturation and the resulting mechanical properties. The kinetics of dissolution can be influenced by various external factors. This work deals with monitoring the carbide dissolution [...] Read more.
The dissolution of carbides during the heating to the quenching temperature has a significant effect on the martensite oversaturation and the resulting mechanical properties. The kinetics of dissolution can be influenced by various external factors. This work deals with monitoring the carbide dissolution utilizing dilatometer analysis. The austenitization of 100CrMnSi6-4 bearing steel in two initial states was compared—after accelerated spheroidization annealing and conventional soft annealing. The main objective was to determine the amount of undissolved cementite during austenitization in the temperature range where only austenite and cementite are present in the structure. The austenitization temperature determines the degree of cementite dissolution and, consequently, the carbon content in austenite and thus the final properties after quenching. The cementite dissolution was quantified from dilatometric curves and image analysis. Full article
(This article belongs to the Special Issue Microstructure and Mechanical Properties Relationship for Metallic Materials)
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13 pages, 7987 KiB  
Article
Fatigue Properties of Spring Steels after Advanced Processing
by Radek Procházka, Adam Stehlík, Jakub Kotous, Pavel Salvetr, Tomasz Bucki, Ondřej Stránský and Sanin Zulić
Materials 2023, 16(9), 3327; https://0-doi-org.brum.beds.ac.uk/10.3390/ma16093327 - 24 Apr 2023
Cited by 3 | Viewed by 1790
Abstract
This article deals with the effect of strain-assisted tempering (SAT) on the fatigue properties of 54SiCr6 steel used for spring steel wires in a wide variety of automotive applications, including coil springs. This steel spring wire is extremely strong, having a high elastic [...] Read more.
This article deals with the effect of strain-assisted tempering (SAT) on the fatigue properties of 54SiCr6 steel used for spring steel wires in a wide variety of automotive applications, including coil springs. This steel spring wire is extremely strong, having a high elastic limit and yield point, giving the steel excellent energy accumulation and fatigue properties. This combination opens up new possibilities in helical and cylindrical coil spring design, resulting in the reduction of both size and weight. Lightweight coil springs lead to improvements in fuel consumption, stability and vehicle traction. A large plastic deformation and SAT were applied to enhance the yield point of the study material. Improvements in the static and cyclic properties of steel springs were investigated using tensile tests and 3PB fatigue tests at ambient temperature. In addition, an advanced laser shock peening (LSP) process was employed to increase the fatigue resistance of the SAT material. The results presented here show great improvements in the static and fatigue properties over commercial steel treatment. The material quality of the wires was evaluated to be insufficient for further processing with cold coiling. Full article
(This article belongs to the Special Issue Microstructure and Mechanical Properties Relationship for Metallic Materials)
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17 pages, 6343 KiB  
Article
Effect of Cu Alloying on Mechanical Properties of Medium-C Steel after Long-Time Tempering at 500 °C
by Pavel Salvetr, Aleksandr Gokhman, Milan Svoboda, Črtomir Donik, Ivana Podstranská, Jakub Kotous and Zbyšek Nový
Materials 2023, 16(6), 2390; https://0-doi-org.brum.beds.ac.uk/10.3390/ma16062390 - 16 Mar 2023
Cited by 4 | Viewed by 1226
Abstract
This research studies the influence of the copper alloying of medium-carbon steel on mechanical properties after quenching and tempering at 500 °C. The microstructure was characterised using SEM, EBSD, TEM, and XRD analysis. The mechanical properties were comprehensively investigated using hardness measurements, tensile [...] Read more.
This research studies the influence of the copper alloying of medium-carbon steel on mechanical properties after quenching and tempering at 500 °C. The microstructure was characterised using SEM, EBSD, TEM, and XRD analysis. The mechanical properties were comprehensively investigated using hardness measurements, tensile and Charpy impact tests and solid solution, grain boundary, dislocation, and precipitation strengthening contributions were estimated. Higher yield strength for Cu-alloyed steel was confirmed at about 35–73 MPa. The precipitation strengthening contribution from Cu precipitates in the range of 11–49 MPa was calculated. The interaction between Cu precipitates and dislocations retards the decrease in dislocation density. Similar values of effective grain size of martensite crystals were measured for Cu-alloyed and Cu-free steel as well. Copper alloyed steel exhibited significantly deteriorated impact toughness, total plastic elongation, and reduction of area. The size of Cu precipitates ranged from 8.3 nm after tempering at 500 °C for 6 h to 13.9 nm after tempering for 48 h. Full article
(This article belongs to the Special Issue Microstructure and Mechanical Properties Relationship for Metallic Materials)
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14 pages, 10047 KiB  
Article
Effect of Double-Step and Strain-Assisted Tempering on Properties of Medium-Carbon Steel
by Pavel Salvetr, Andrea Školáková, Jakub Kotous, Jan Drahokoupil, Daniel Melzer, Zdeněk Jansa, Črtomir Donik, Aleksandr Gokhman and Zbyšek Nový
Materials 2023, 16(5), 2121; https://0-doi-org.brum.beds.ac.uk/10.3390/ma16052121 - 06 Mar 2023
Cited by 2 | Viewed by 1435
Abstract
The present work aimed to study the properties of medium-carbon steel during tempering treatment and to present the strength increase of medium-carbon spring steels by strain-assisted tempering (SAT). The effect of double-step tempering and double-step tempering with rotary swaging, also known as SAT, [...] Read more.
The present work aimed to study the properties of medium-carbon steel during tempering treatment and to present the strength increase of medium-carbon spring steels by strain-assisted tempering (SAT). The effect of double-step tempering and double-step tempering with rotary swaging, also known as SAT, on the mechanical properties and microstructure was investigated. The main goal was to achieve a further enhancement of the strength of medium-carbon steels using SAT treatment. The microstructure consists of tempered martensite with transition carbides in both cases. The yield strength of the DT sample is 1656 MPa, while that of the SAT sample is about 400 MPa higher. On the contrary, plastic properties such as the elongation and reduction in area have lower values after SAT processing, about 3% and 7%, respectively, compared to the DT treatment. Grain boundary strengthening from low-angle grain boundaries can be attributed to the increase in strength. Based on X-ray diffraction analysis, a lower dislocation strengthening contribution was determined for the SAT sample compared to the double-step tempered sample. Full article
(This article belongs to the Special Issue Microstructure and Mechanical Properties Relationship for Metallic Materials)
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12 pages, 5344 KiB  
Article
Effect of Heat Treatment on Creep Deformation and Fracture Properties for a Coarse-Grained Inconel 718 Manufactured by Directed Energy Deposition
by Ying Li, Pavel Podaný, Martina Koukolíková, Jan Džugan, Tomáš Krajňák, Jozef Veselý and Srinivasan Raghavan
Materials 2023, 16(4), 1377; https://0-doi-org.brum.beds.ac.uk/10.3390/ma16041377 - 06 Feb 2023
Cited by 3 | Viewed by 1375
Abstract
The creep properties of a laser-directed energy deposition (L-DED) technique manufactured Inconel 718 (IN718) was investigated at 650 °C/700 MPa. Microstructure and creep properties of L-DED IN718 samples were tailored by various post heat treatments involving homogenization heat treatment with temperature ranging from [...] Read more.
The creep properties of a laser-directed energy deposition (L-DED) technique manufactured Inconel 718 (IN718) was investigated at 650 °C/700 MPa. Microstructure and creep properties of L-DED IN718 samples were tailored by various post heat treatments involving homogenization heat treatment with temperature ranging from 1080 to 1180 °C + double aging and hot isostatic pressing (HIP). Microstructural changes and their influence on the creep behavior and fracture mechanism were observed and discussed. The results show that L-DED sample heat treated by a simple double aging exhibits a 49% increase in creep lifetime tr and a comparable creep elongation ɛf when compared to the wrought material, due to the reserved coarse dislocation cell substructure from the L-DED process. The loss of dislocation cell structure and the coarsening of grains at higher temperature of heat treatments contributes to a shorter tr, εf, but faster ε̇min (minimum creep rate). The present work demonstrates that a simultaneous improvement of creep strength and creep elongation can be achieved in the case of a coarse-grained L-DED IN718 by a double aging treatment which can preserve both the strengthening precipitates and an appropriate size of dislocation cells. Full article
(This article belongs to the Special Issue Microstructure and Mechanical Properties Relationship for Metallic Materials)
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16 pages, 14162 KiB  
Article
Interfacial Adhesion of Thick NiTi Coating on Substrate Stainless Steel
by Sneha Samal, Jaromír Kopeček and Petr Šittner
Materials 2022, 15(23), 8598; https://0-doi-org.brum.beds.ac.uk/10.3390/ma15238598 - 02 Dec 2022
Cited by 8 | Viewed by 1060
Abstract
Interfacial adhesion of thick NiTi coating on substrate stainless steel is investigated here. NiTi coating was deposited on the substrate by using the thermal plasma spraying method. Deposition of NiTi coating was carried out by using various levels of input power under an [...] Read more.
Interfacial adhesion of thick NiTi coating on substrate stainless steel is investigated here. NiTi coating was deposited on the substrate by using the thermal plasma spraying method. Deposition of NiTi coating was carried out by using various levels of input power under an Ar atmosphere. Multiple coating layers were deposited on the stainless steel surface for a specific thickness. The cross-section of the plasma-sprayed samples were prepared and characterized by using various techniques. The hardness of the coating layers on the surface and cross-section was examined. The thickness of the coating increased with the increase in power. No cracks were detected in the interface for the NiTi coating deposited at 12 kW power. However minor pores were observed at some regions along the interface at the sample prepared at 9 kW power. A good-quality coating layer was formed at the interface of the substrate. Primary phases of austenite and martensite were confirmed from the EBSD and XRD investigations. There was the presence of intermetallic and oxide phases in the coating layers. A less heat-affected zone of 10 µm of along the interface was confirmed without any diffusion of elements from the substrate to the coating layers. There was homogenous distribution elemental composition of Ni and Ti throughout the coating layers. Full article
(This article belongs to the Special Issue Microstructure and Mechanical Properties Relationship for Metallic Materials)
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19 pages, 7935 KiB  
Article
Enhanced Spring Steel’s Strength Using Strain Assisted Tempering
by Zbyšek Nový, Pavel Salvetr, Jakub Kotous, Petr Motyčka, Aleksandr Gokhman, Črtomir Donik and Ján Džugan
Materials 2022, 15(20), 7354; https://0-doi-org.brum.beds.ac.uk/10.3390/ma15207354 - 20 Oct 2022
Cited by 4 | Viewed by 1356
Abstract
Spring steels are typical materials where enhancement of mechanical properties can save considerable mass for transport vehicles, in this way the consumption of fuel or electric energy can be decreased. A drastic change in both the resulting microstructure and mechanical properties could be [...] Read more.
Spring steels are typical materials where enhancement of mechanical properties can save considerable mass for transport vehicles, in this way the consumption of fuel or electric energy can be decreased. A drastic change in both the resulting microstructure and mechanical properties could be achieved due to the inclusion of strain into the tempering process after quenching. The strain assisted tempering (SAT) technology was applied, i.e., the process of quenching and following a sequence of tempering operations alternating with strain operations. After the first tempering, controlled deformation by rotary swaging was carried out with a strain of 17% (strain rate is about 120 s−1). Considerably higher strength parameters after SAT compared to conventional quenching and tempering (QT) technology were nevertheless accompanied by enhanced notch toughness at the same time by the decrease of elongation and reduction of area. However, by optimizing the process it is was also possible to achieve acceptable values for those parameters. Remarkable differences are visible in resulting microstructures of compared samples, which were revealed by metallographic analysis and X-ray diffraction measurement. While the standard microstructure of tempered martensite with transition carbides was observed after QT processing, carbideless islands with nanotwins occurred in martensitic laths after SAT processing. Full article
(This article belongs to the Special Issue Microstructure and Mechanical Properties Relationship for Metallic Materials)
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13 pages, 7332 KiB  
Article
Influence of EDM Process Parameters on the Surface Finish of Alnico Alloys
by Damian Bańkowski and Piotr Młynarczyk
Materials 2022, 15(20), 7277; https://0-doi-org.brum.beds.ac.uk/10.3390/ma15207277 - 18 Oct 2022
Cited by 6 | Viewed by 1447
Abstract
This article deals with electrical discharge machining (EDM) of an alnico alloy, focusing on how key process parameters affect the surface finish. The experiments were conducted using a BP93L EDM machine. The Box–Behnken design was employed to study the effects of three factors, [...] Read more.
This article deals with electrical discharge machining (EDM) of an alnico alloy, focusing on how key process parameters affect the surface finish. The experiments were conducted using a BP93L EDM machine. The Box–Behnken design was employed to study the effects of three factors, i.e., spark current, pulse-on time, and pulse-off time, each at three levels, on the surface quality. A specially designed system was employed to increase the effectiveness of the machining process by imparting an additional rotary motion to the tool and an additional rotary motion to the workpiece. The aim was to efficiently remove the eroded metal particles and create a surface with smaller craters. The workpiece surface roughness was measured with a Talysurf CCI lite non-contact profiler. During this precision machining process, the arithmetical mean height (Sa) was less than 1 µm. The surface quality was examined also using scanning electron microscopy (SEM) and optical microscopy (OM). The experimental data were analyzed by means of Statistica to determine and graphically represent the relationships between the input and output parameters. Full article
(This article belongs to the Special Issue Microstructure and Mechanical Properties Relationship for Metallic Materials)
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20 pages, 9322 KiB  
Article
The Use of Miniature Specimens to Determine Local Properties and Fracture Behavior of LPBF-Processed Inconel 718 in as-Deposited and Post-Treated States
by Jan Dzugan, Mohsen Seifi, Martin Rund, Pavel Podany, Richard Grylls and John J. Lewandowski
Materials 2022, 15(13), 4724; https://0-doi-org.brum.beds.ac.uk/10.3390/ma15134724 - 05 Jul 2022
Cited by 3 | Viewed by 1620
Abstract
This paper summarizes the assessment of directional anisotropy in local mechanical properties for Laser Powder Bed Fusion (LPBF) IN-718 bulk samples via the use of miniature samples excised from the bulk for both as-deposited and post-treated states. The quasi-static tensile properties at room [...] Read more.
This paper summarizes the assessment of directional anisotropy in local mechanical properties for Laser Powder Bed Fusion (LPBF) IN-718 bulk samples via the use of miniature samples excised from the bulk for both as-deposited and post-treated states. The quasi-static tensile properties at room temperature are investigated at several different locations along the build direction and at different orientations for both considered states. A comparison between the excised miniature tensile specimens and standard-sized sample results have also been conducted and exhibit very good agreement. Significant anisotropy is present in mechanical properties at different build heights for the as-deposited state, while the post-treated material exhibited more homogenous properties, both along the height and for different sampling orientations. However, significant reductions (e.g., >30%) in the strength (Yield, UTS) along with a significant increase in the reduction in area at fracture is found for post-processed materials. Metallography and fractography analyses were conducted in order to begin to determine the source(s) of this anisotropy for the as-deposited state. Full article
(This article belongs to the Special Issue Microstructure and Mechanical Properties Relationship for Metallic Materials)
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17 pages, 6120 KiB  
Article
Elevated Temperature Baseplate Effect on Microstructure, Mechanical Properties, and Thermal Stress Evaluation by Numerical Simulation for Austenite Stainless Steel 316L Fabricated by Directed Energy Deposition
by Abhilash Kiran, Ying Li, Martina Koukolíková, Michal Brázda, Josef Hodek, Miroslav Urbánek, Ján Džugan, Srinivasan Raghavan and Josef Odehnal
Materials 2022, 15(12), 4165; https://0-doi-org.brum.beds.ac.uk/10.3390/ma15124165 - 12 Jun 2022
Cited by 6 | Viewed by 1583
Abstract
In the present study, the effect of material deposition at the elevated temperature baseplate on the microstructure and mechanical properties was investigated and correlated to the unique thermal history by using numerical simulation. Numerical results agreed well with the experimental results of microstructure [...] Read more.
In the present study, the effect of material deposition at the elevated temperature baseplate on the microstructure and mechanical properties was investigated and correlated to the unique thermal history by using numerical simulation. Numerical results agreed well with the experimental results of microstructure and mechanical properties. Numerical results revealed a significant decrease in temperature gradient and a 40% decrease in thermal stress due to material deposition on the elevated temperature baseplate. The reduced thermal stress and temperature gradient resulted in coarser grain features, which in turn led to a decrease in hardness and tensile strength, especially for the bottom region near the baseplate. Meanwhile, no significant effect could be found for ductility. In addition, an elevated temperature baseplate promoted less heterogeneity in hardness and tensile properties along the building direction. The current work demonstrates a collective and direct understanding of the baseplate preheating effect on thermal stress, microstructure and mechanical properties and their correlations, which is believed beneficial for the better utilization of baseplate preheating positive effects. Full article
(This article belongs to the Special Issue Microstructure and Mechanical Properties Relationship for Metallic Materials)
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13 pages, 2066 KiB  
Article
Extended Continuous Cooling Transformation (CCT) Diagrams Determination for Additive Manufacturing Deposited Steels
by Kristýna Halmešová, Radek Procházka, Martina Koukolíková, Jan Džugan, Pavel Konopík and Tomasz Bucki
Materials 2022, 15(9), 3076; https://0-doi-org.brum.beds.ac.uk/10.3390/ma15093076 - 23 Apr 2022
Cited by 6 | Viewed by 2647
Abstract
Continuous cooling transformation (CCT) diagrams are widely used when heat treating steels and represent which type of phase will occur in a material as it is cooled at different cooling rates. CCT diagrams are constructed on the basis of dilatometry measurements on relatively [...] Read more.
Continuous cooling transformation (CCT) diagrams are widely used when heat treating steels and represent which type of phase will occur in a material as it is cooled at different cooling rates. CCT diagrams are constructed on the basis of dilatometry measurements on relatively small testing samples (cylindrical shape with diameter of 4mm and length of 11 mm in this study). The main aim of this work was to demonstrate the possibility of evaluating the tensile test properties using mini-tensile tests from miniature volumes (1.4 × 10−7 m3 for one sample) subsequent to determination of the CCT diagram and to extend a standard CCT diagram with information about strength, ductility and the estimated value of the work-hardening coefficient. Mini-tensile tests (MTT) were recently developed due to the low availability of experimental material and have already been successfully used for local mechanical property characterization of metals. CCT diagrams were constructed for 42CrMo4 steel prepared by the laser-directed energy deposition (L-DED) process, for commercially available 42CrMo4 steel conventionally manufactured (for comparison of traditional processing and AM preparation) and for H13 tool steel deposited by the selective laser melting (SLM) process. Full article
(This article belongs to the Special Issue Microstructure and Mechanical Properties Relationship for Metallic Materials)
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23 pages, 8727 KiB  
Article
Heat Source Modeling and Residual Stress Analysis for Metal Directed Energy Deposition Additive Manufacturing
by Abhilash Kiran, Ying Li, Josef Hodek, Michal Brázda, Miroslav Urbánek and Jan Džugan
Materials 2022, 15(7), 2545; https://0-doi-org.brum.beds.ac.uk/10.3390/ma15072545 - 30 Mar 2022
Cited by 13 | Viewed by 3142
Abstract
The advancement in additive manufacturing encourages the development of simplified tools for deep and swift research of the technology. Several approaches were developed to reduce the complexity of multi-track modeling for additive manufacturing. In the present work, a simple heat source model called [...] Read more.
The advancement in additive manufacturing encourages the development of simplified tools for deep and swift research of the technology. Several approaches were developed to reduce the complexity of multi-track modeling for additive manufacturing. In the present work, a simple heat source model called concentrated heat source was evaluated for single- and multi-track deposition for directed energy deposition. The concentrated heat source model was compared with the widely accepted Goldak heat source model. The concentrated heat source does not require melt pool dimension measurement for thermal model simulation. Thus, it reduces the considerable time for preprocessing. The shape of the melt pool and temperature contour around the heat source was analyzed for single-track deposition. A good agreement was noticed for the concentrated heat source model melt pool, with an experimentally determined melt pool, using an optical microscope. Two heat source models were applied to multi-track 3D solid structure thermo-mechanical simulation. The results of the two models, for thermal history and residual stress, were compared with experimentally determined data. A good agreement was found for both models. The concentrated heat source model reported less than the half the computational time required for the Goldak model. The validated model, for 3D solid structure thermo-mechanical simulation, was used to analyze thermal stress evolution during the deposition process. The material deposition on the base plate at room temperature results in lower peak temperatures in the layers near the base plate. Consequently, the higher thermal stress in the layers near the base plate was found, compared to the upper layers during the deposition process. Full article
(This article belongs to the Special Issue Microstructure and Mechanical Properties Relationship for Metallic Materials)
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18 pages, 5006 KiB  
Article
Characterization of the Interface between Aluminum and Iron in Co-Extruded Semi-Finished Products
by Susanne Elisabeth Thürer, Kai Peters, Torsten Heidenblut, Norman Heimes, Julius Peddinghaus, Florian Nürnberger, Bernd-Arno Behrens, Hans Jürgen Maier and Christian Klose
Materials 2022, 15(5), 1692; https://0-doi-org.brum.beds.ac.uk/10.3390/ma15051692 - 24 Feb 2022
Cited by 1 | Viewed by 1687
Abstract
Within the framework of the Collaborative Research Center 1153, we investigated novel process chains for the production of bulk components with different metals as joining partners. In the present study, the co-extrusion of coaxially reinforced hollow profiles was employed to manufacture semi-finished products [...] Read more.
Within the framework of the Collaborative Research Center 1153, we investigated novel process chains for the production of bulk components with different metals as joining partners. In the present study, the co-extrusion of coaxially reinforced hollow profiles was employed to manufacture semi-finished products for a subsequent die-forging process, which was then used for the manufacture of hybrid bearing bushings. The hybrid hollow profiles, made of the aluminum alloy EN AW-6082 paired with either the case-hardening steel 20MnCr5, the stainless steel X5CrNi18-10, or the rolling bearing steel 100Cr6, were produced by Lateral Angular Co-Extrusion. Push-out tests on hybrid hollow sections over the entire sample cross-section showed shear strengths of 44 MPa ± 8 MPa (100Cr6) up to 63 MPa ± 5 MPa (X5CrNi18-10). In particular, the influence of force and form closure on the joint zone could be determined using specimen segments tested in shear compression. Locally, shear strengths of up to 131 MPa (X5CrNi18-10) were demonstrated in the shear compression test. From these samples, lamellae for microstructural analysis were prepared with a Focused Ion Beam. Detailed analyses showed that for all material combinations, a material bond in the form of an ultra-thin intermetallic phase seam with a thickness of up to 50 nm could be established. Full article
(This article belongs to the Special Issue Microstructure and Mechanical Properties Relationship for Metallic Materials)
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20 pages, 2876 KiB  
Article
A Data-Driven Approach for Studying the Influence of Carbides on Work Hardening of Steel
by Martina Vittorietti, Javier Hidalgo, Jesús Galán López, Jilt Sietsma and Geurt Jongbloed
Materials 2022, 15(3), 892; https://0-doi-org.brum.beds.ac.uk/10.3390/ma15030892 - 24 Jan 2022
Cited by 1 | Viewed by 2821
Abstract
This study proposes a new approach to determine phenomenological or physical relations between microstructure features and the mechanical behavior of metals bridging advanced statistics and materials science in a study of the effect of hard precipitates on the hardening of metal alloys. Synthetic [...] Read more.
This study proposes a new approach to determine phenomenological or physical relations between microstructure features and the mechanical behavior of metals bridging advanced statistics and materials science in a study of the effect of hard precipitates on the hardening of metal alloys. Synthetic microstructures were created using multi-level Voronoi diagrams in order to control microstructure variability and then were used as samples for virtual tensile tests in a full-field crystal plasticity solver. A data-driven model based on Functional Principal Component Analysis (FPCA) was confronted with the classical Voce law for the description of uniaxial tensile curves of synthetic AISI 420 steel microstructures consisting of a ferritic matrix and increasing volume fractions of M23C6 carbides. The parameters of the two models were interpreted in terms of carbide volume fractions and texture using linear mixed-effects models. Full article
(This article belongs to the Special Issue Microstructure and Mechanical Properties Relationship for Metallic Materials)
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11 pages, 5768 KiB  
Article
Substantial Improvement of High Temperature Strength of New-Generation Nano-Oxide-Strengthened Alloys by Addition of Metallic Yttrium
by Jiří Svoboda, Petr Bořil, Jakub Holzer, Natália Luptáková, Milan Jarý, Bohuslav Mašek and Petr Dymáček
Materials 2022, 15(2), 504; https://0-doi-org.brum.beds.ac.uk/10.3390/ma15020504 - 10 Jan 2022
Cited by 10 | Viewed by 1359
Abstract
Oxide-dispersion-strengthened (ODS) Fe-Al-Y2O3-based alloys (denoted as FeAlOY) containing 5 vol. % of nano-oxides have a potential to become top oxidation and creep-resistant alloys for applications at temperatures of 1100–1300 °C. Oxide dispersoids cause nearly perfect strengthening of grains; thus, [...] Read more.
Oxide-dispersion-strengthened (ODS) Fe-Al-Y2O3-based alloys (denoted as FeAlOY) containing 5 vol. % of nano-oxides have a potential to become top oxidation and creep-resistant alloys for applications at temperatures of 1100–1300 °C. Oxide dispersoids cause nearly perfect strengthening of grains; thus, grain boundaries with limited cohesive strength become the weak link in FeAlOY in this temperature range. One of the possibilities for significantly improving the strength of FeAlOY is alloying with appropriate elements and increasing the cohesive strength of grain boundaries. Nearly 20 metallic elements have been tested with the aim to increase cohesive strength in the frame of preliminary tests. A positive influence is revealed for Al, Cr, and Y, whereby the influence of Y is enormous (addition of 1% of metallic Y increases strength by a factor of 2), as it is presented in this paper. Full article
(This article belongs to the Special Issue Microstructure and Mechanical Properties Relationship for Metallic Materials)
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17 pages, 4071 KiB  
Article
The Positive Role of Nanometric Molybdenum–Vanadium Carbides in Mitigating Hydrogen Embrittlement in Structural Steels
by Luis Borja Peral, Inés Fernández-Pariente, Chiara Colombo, Cristina Rodríguez and Javier Belzunce
Materials 2021, 14(23), 7269; https://0-doi-org.brum.beds.ac.uk/10.3390/ma14237269 - 28 Nov 2021
Cited by 11 | Viewed by 1648
Abstract
The influence of hydrogen on the fracture toughness and fatigue crack propagation rate of two structural steel grades, with and without vanadium, was evaluated by means of tests performed on thermally precharged samples in a hydrogen reactor at 195 bar and 450 °C [...] Read more.
The influence of hydrogen on the fracture toughness and fatigue crack propagation rate of two structural steel grades, with and without vanadium, was evaluated by means of tests performed on thermally precharged samples in a hydrogen reactor at 195 bar and 450 °C for 21 h. The degradation of the mechanical properties was directly correlated with the interaction between hydrogen atoms and the steel microstructure. A LECO DH603 hydrogen analyzer was used to study the activation energies of the different microstructural trapping sites, and also to study the hydrogen eggresion kinetics at room temperature. The electrochemical hydrogen permeation technique was employed to estimate the apparent hydrogen diffusion coefficient. Under the mentioned hydrogen precharging conditions, a very high hydrogen concentration was introduced within the V-added steel (4.3 ppm). The V-added grade had stronger trapping sites and much lower apparent diffusion coefficient. Hydrogen embrittlement susceptibility increased significantly due to the presence of internal hydrogen in the V-free steel in comparison with tests carried out in the uncharged condition. However, the V-added steel grade (+0.31%V) was less sensitive to hydrogen embrittlement. This fact was ascribed to the positive effect of the precipitated nanometric (Mo,V)C to alleviate hydrogen embrittlement. Mixed nanometric (Mo,V)C might be considered to be nondiffusible hydrogen-trapping sites, in view of their strong hydrogen-trapping capability (~35 kJ/mol). Hence, mechanical behavior of the V-added grade in the presence of internal hydrogen was notably improved. Full article
(This article belongs to the Special Issue Microstructure and Mechanical Properties Relationship for Metallic Materials)
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19 pages, 8308 KiB  
Article
Effect of 1.5 wt% Copper Addition and Various Contents of Silicon on Mechanical Properties of 1.7102 Medium Carbon Steel
by Pavel Salvetr, Aleksandr Gokhman, Zbyšek Nový, Petr Motyčka and Jakub Kotous
Materials 2021, 14(18), 5244; https://0-doi-org.brum.beds.ac.uk/10.3390/ma14185244 - 12 Sep 2021
Cited by 9 | Viewed by 1823
Abstract
Requirements for mechanical properties of steels are constantly increasing, and the combination of quenching and tempering is the method generally chosen for achieving high strength in medium carbon steels. This study examines the influence of various silicon contents from 1.06 to 2.49 wt% [...] Read more.
Requirements for mechanical properties of steels are constantly increasing, and the combination of quenching and tempering is the method generally chosen for achieving high strength in medium carbon steels. This study examines the influence of various silicon contents from 1.06 to 2.49 wt% and the addition of copper (1.47 wt%) on the behavior of 1.7102 steel starting with the as-quenched state and ending with the tempered condition at the temperature of 500 °C. The microstructure was characterized by SEM and TEM, the phase composition and dislocation density were studied by XRD analysis, and mechanical properties were assessed by tensile and hardness testing, whereas tempered martensite embrittlement was assessed using Charpy impact test and the activation energy of carbide precipitation was determined by dilatometry. The benefit of copper consists in the improvement of reduction of area by tempering between 150 and 300 °C. The increase in strength due to copper precipitation occurs upon tempering at 500 °C, where strength is generally low due to a drop in dislocation density and changes in microstructure. The increasing content of silicon raises strength and dislocation density in steels, but the plastic properties of steel are limited. It was found that the silicon content of 1.5 wt% is optimum for the materials under study. Full article
(This article belongs to the Special Issue Microstructure and Mechanical Properties Relationship for Metallic Materials)
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10 pages, 2339 KiB  
Article
Plastic Instability in Medium-Carbon Tempered Martensite Steel
by Hai Qiu, Rintaro Ueji, Tadanobu Inoue and Yuuji Kimura
Materials 2021, 14(16), 4609; https://0-doi-org.brum.beds.ac.uk/10.3390/ma14164609 - 17 Aug 2021
Cited by 1 | Viewed by 1549
Abstract
Inhomogeneous plastic deformation damages the surface quality of a product in the metal forming process. Therefore, it is necessary to investigate the plastic instability of a metal. Tempered martensite is a common microstructure of medium-carbon steel. Plastic instability (Lüders phenomenon, Portevin-Le Châtelier phenomenon) [...] Read more.
Inhomogeneous plastic deformation damages the surface quality of a product in the metal forming process. Therefore, it is necessary to investigate the plastic instability of a metal. Tempered martensite is a common microstructure of medium-carbon steel. Plastic instability (Lüders phenomenon, Portevin-Le Châtelier phenomenon) in this phase was investigated by a uniaxial tension test performed at room temperature. The formation and propagation of a plastic band were analyzed via two-dimensional digital image correlation, and the strain and strain-rate fields were experimentally evaluated. The results obtained are as follows: (1) there was no clear yield plateau on the stress–strain curve; (2) Lüders phenomenon was present, but the Portevin-Le Châtelier phenomenon was not found; (3) in the Lüders deformation process, local strain distribution in tempered martensite is more complicated than that in ferrite. Full article
(This article belongs to the Special Issue Microstructure and Mechanical Properties Relationship for Metallic Materials)
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14 pages, 71606 KiB  
Article
Copper-Induced Strengthening in 0.2 C Bainite Steel
by Jaromir Dlouhy, Pavel Podany and Jan Dzugan
Materials 2021, 14(8), 1962; https://0-doi-org.brum.beds.ac.uk/10.3390/ma14081962 - 14 Apr 2021
Viewed by 1499
Abstract
Bainitic steels were the focus of this study. These steels have the potential to obtain a good combination of strength, ductility, and edge stretchability, which is a very desirable characteristic in the automotive industry. Cu precipitation potential was investigated during prolonged isothermal bainitization [...] Read more.
Bainitic steels were the focus of this study. These steels have the potential to obtain a good combination of strength, ductility, and edge stretchability, which is a very desirable characteristic in the automotive industry. Cu precipitation potential was investigated during prolonged isothermal bainitization treatment. Precipitation strengthening and ductility were measured using a tensile test, and edge stretchability was measured using a hole expansion test. The microstructure was characterized by high-resolution scanning electron microscopy and an electron backscattered diffraction. Lower bainite was obtained by austenitization treatment and subsequent immersion into a salt bath at 400 °C. Cu precipitation occurred after 120 min of holding in the bath and enhanced the yield stress of the Cu-alloyed steel by 120 MPa as compared with a reference steel without Cu. The strengthening did not affect ductility and decreased the edge stretchability by 10%. Steels with different Mn contents were examined. It was found that the enhancement of Mn content from 1 to 2 wt.% did not boost Cu strengthening ability. This result showed that the presence of Mn did not cause an Mn-Cu precipitation strengthening synergy, observed previously during martensite tempering procedure. Full article
(This article belongs to the Special Issue Microstructure and Mechanical Properties Relationship for Metallic Materials)
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20 pages, 6413 KiB  
Article
The Effect of the β-Al5FeSi Phases on Microstructure, Mechanical and Fatigue Properties in A356.0 Cast Alloys with Higher Fe Content without Additional Alloying of Mn
by Lenka Kuchariková, Denisa Medvecká, Eva Tillová, Juraj Belan, Michaela Kritikos, Mária Chalupová and Milan Uhríčik
Materials 2021, 14(8), 1943; https://0-doi-org.brum.beds.ac.uk/10.3390/ma14081943 - 13 Apr 2021
Cited by 10 | Viewed by 2194
Abstract
Secondary-cast aluminum alloys have increasing industrial applications. Their biggest deficiency is their impurity content, especially Fe, which has low solubility in Al and almost all the content creates intermetallic phases. This work examines the effect of higher Fe content on the microstructure and [...] Read more.
Secondary-cast aluminum alloys have increasing industrial applications. Their biggest deficiency is their impurity content, especially Fe, which has low solubility in Al and almost all the content creates intermetallic phases. This work examines the effect of higher Fe content on the microstructure and properties of A356.0 alloy. At the same time, no other possibility existed to affecting the brittleness of the formation of the β phases. The calculation of Fecrit, ratio of Mn/Fe, quantitative and computed tomography analysis of porosity and Fe plate-like phases, measurement of mechanical and fatigue properties, and fractography analysis were performed in this study. The results show that gravity die casting into a sand mold, and the non-usage of Mn addition or heat treatment, do not have a negative effect on increasing the size of the Fe-rich plate-like phases. The longest Fe-rich phases have limited the pore growth and ratios, but their higher thickness led to greater porosity formation. The mechanical and fatigue properties correlate with the Fecrit level and the highest were for the experimental alloy with 0.454 wt.% of Fe. The experimental results confirmed the fact that if the Fe plate-like phases have a length of up to 50 µm, the fatigue properties depend more on the size of porosity. If the length of the Fe needles is more than 50 µm, then the properties are mainly affected by the length of these Fe phases. Full article
(This article belongs to the Special Issue Microstructure and Mechanical Properties Relationship for Metallic Materials)
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13 pages, 2688 KiB  
Article
Grain-to-Grain Interaction Effect in Polycrystalline Plain Low-Carbon Steel within Elastic Deformation Region
by Hai Qiu, Rintaro Ueji, Yuuji Kimura and Tadanobu Inoue
Materials 2021, 14(8), 1865; https://0-doi-org.brum.beds.ac.uk/10.3390/ma14081865 - 09 Apr 2021
Cited by 1 | Viewed by 1676
Abstract
A grain is surrounded by grains with different crystal orientations in polycrystalline plain low-carbon steel. The grain is constrained by its adjacent grains in the tension process. The interaction of the grain with the adjacent grains was investigated within the elastic deformation region. [...] Read more.
A grain is surrounded by grains with different crystal orientations in polycrystalline plain low-carbon steel. The grain is constrained by its adjacent grains in the tension process. The interaction of the grain with the adjacent grains was investigated within the elastic deformation region. The following results have been obtained: (1) the Young’s modulus of a grain without consideration of grain-to-grain interaction is denoted as the inherent Young’s modulus; when the inherent Young’s modulus of a grain is equal to the Young’s modulus of the bulk material, there is almost no interaction between the grain and its adjacent grains; when a grain has a great difference between its inherent Young’s modulus and the Young’s modulus of the bulk material, its grain-to-grain interactions increase significantly; (2) the grain-to-grain interaction is mainly caused by the difference in the inherent Young’s modulus between the grain and its adjacent grains; the misorientation angle between the grain and its adjacent grains has almost no effect on the grain-to-grain interaction. Full article
(This article belongs to the Special Issue Microstructure and Mechanical Properties Relationship for Metallic Materials)
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13 pages, 7837 KiB  
Article
The Performance of CR180IF and DP600 Laser Welded Steel Sheets under Different Strain Rates
by Mária Mihaliková, Kristína Zgodavová, Peter Bober and Anna Špegárová
Materials 2021, 14(6), 1553; https://0-doi-org.brum.beds.ac.uk/10.3390/ma14061553 - 22 Mar 2021
Cited by 8 | Viewed by 1962
Abstract
The presented research background is a car body manufacturer’s request to test the car body’s components welded from dissimilar steel sheets. In view of the vehicle crew’s protection, it is necessary to study the static and dynamic behavior of welded steels. Therefore, the [...] Read more.
The presented research background is a car body manufacturer’s request to test the car body’s components welded from dissimilar steel sheets. In view of the vehicle crew’s protection, it is necessary to study the static and dynamic behavior of welded steels. Therefore, the influence of laser welding on the mechanical and dynamical properties, microstructure, microhardness, and welded joint surface roughness of interstitial free CR180IF and dual-phase DP600 steels were investigated. Static tensile tests were carried out by using testing machine Zwick 1387, and dynamic test used rotary hammer machine RSO. Sheet steel was tested at different strain rates ranging from 10−3 to 103 s−1. The laser welds’ microstructure and microhardness were evaluated in the base metal, heat-affected zone, and fusion zone. The comprehensive analysis also included chemical analysis, fracture surface analysis, and roughness measurement. The research results showed that the strain rate had an influence on the mechanical properties of base materials and welded joints. The dynamic loading increases the yield stress more than the ultimate tensile strength for the monitored steels, while the most significant increase was recorded for the welded material. Full article
(This article belongs to the Special Issue Microstructure and Mechanical Properties Relationship for Metallic Materials)
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17 pages, 7273 KiB  
Article
Strain Hardening in an AZ31 Alloy Submitted to Rotary Swaging
by Zuzanka Trojanová, Zdeněk Drozd, Kristýna Halmešová, Ján Džugan, Tomáš Škraban, Peter Minárik, Gergely Németh and Pavel Lukáč
Materials 2021, 14(1), 157; https://0-doi-org.brum.beds.ac.uk/10.3390/ma14010157 - 31 Dec 2020
Cited by 10 | Viewed by 1960
Abstract
An extruded magnesium AZ31 magnesium alloy was processed by rotary swaging (RSW) and then deformed by tension and compression at room temperature. The work-hardening behaviour of 1–5 times swaged samples was analysed using Kocks-Mecking plots. Accumulation of dislocations on dislocation obstacles and twin [...] Read more.
An extruded magnesium AZ31 magnesium alloy was processed by rotary swaging (RSW) and then deformed by tension and compression at room temperature. The work-hardening behaviour of 1–5 times swaged samples was analysed using Kocks-Mecking plots. Accumulation of dislocations on dislocation obstacles and twin boundaries is the deciding factor for the strain hardening. Profuse twinning in compression seems to be the reason for the higher hardening observed during compression. The main softening mechanism is apparently the cross-slip between the pyramidal planes of the second and first order. A massive twinning observed at the deformation beginning influences the Hall-Petch parameters. Full article
(This article belongs to the Special Issue Microstructure and Mechanical Properties Relationship for Metallic Materials)
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11 pages, 4396 KiB  
Article
Post-Processing Treatment Impact on Mechanical Properties of SLM Deposited Ti-6Al-4 V Porous Structure for Biomedical Application
by Eren Pehlivan, Jan Džugan, Jaroslav Fojt, Radek Sedláček, Sylwia Rzepa and Matej Daniel
Materials 2020, 13(22), 5167; https://0-doi-org.brum.beds.ac.uk/10.3390/ma13225167 - 16 Nov 2020
Cited by 16 | Viewed by 2936
Abstract
Additive manufacturing technologies allow producing a regular three-dimensional mesh of interconnected struts that form an open-cell porous structure. Regular porous structures have been used in the orthopedic industry due to outstanding bone anchoring. The aim of the study was to determine how the [...] Read more.
Additive manufacturing technologies allow producing a regular three-dimensional mesh of interconnected struts that form an open-cell porous structure. Regular porous structures have been used in the orthopedic industry due to outstanding bone anchoring. The aim of the study was to determine how the postprocessing influences the mechanical properties of porous structures made of titanium alloy CL 41TI ELI. The effect of hot isostatic pressing (HIP) as a method of increasing microstructural integrity was investigated here. The influence of surface etching (SE) technique, which was applied to the porous structure for cleaning unmelted titanium powder particles on the surface of connectors from the inner surfaces of a porous structure, was examined in this study. Mechanical properties were investigated by means of compression tests. The results point out that HIP has a minor effect on the mechanical behavior of considered porous structures. The SE is an effective method to clean the surface of a porous structure, which is very important in the case of biomedical applications when loose powder can cause serious health problems. Another effect of the SE is also the strut thickness reduction. Reducing strut thickness of a porous structure with the surface etching decreases its stiffness to the same extent as predicted by the relative density theoretical model but did not result in structural damage. Full article
(This article belongs to the Special Issue Microstructure and Mechanical Properties Relationship for Metallic Materials)
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10 pages, 1801 KiB  
Article
Quasi-Situ Characterization of Retained Austenite Orientation in Quenching and Partitioning Steel via Uniaxial Tensile Tests
by Pengfei Gao, Jie Liu, Weijian Chen, Feng Li, Jingyu Pang and Zhengzhi Zhao
Materials 2020, 13(20), 4609; https://0-doi-org.brum.beds.ac.uk/10.3390/ma13204609 - 16 Oct 2020
Cited by 2 | Viewed by 1609
Abstract
As a representative of the third generation of advanced high strength steel, the quenching and partitioning steel has excellent potential in automobile manufacturing. The characterization and analysis of the mechanical properties and microstructure of the quenching and partitioning steel during deformation is an [...] Read more.
As a representative of the third generation of advanced high strength steel, the quenching and partitioning steel has excellent potential in automobile manufacturing. The characterization and analysis of the mechanical properties and microstructure of the quenching and partitioning steel during deformation is an effective way to explore the microstructure evolution and transformation-induced plasticity effects of complex phase steels. The relationship between the microstructure morphology and mechanical properties of a 1180 MPa-grade quenching and partitioning steel was investigated through interrupted uniaxial tensile tests plus quasi-situ electron backscatter diffraction measurements. A mixture of ferrite, martensite, and retained austenite was observed in the microstructure. It was found that the volume fraction of global retained austenite decreased linearly with the increase of displacement (0 mm–1.05 mm). The evolution of the retained austenite with typical crystal direction ranges with deformation was characterized. Results show that the orientation (111) and (311) account for the highest proportion of retained austenite grains in the undeformed sample and the mechanical stability of the (311) retained austenite grains is the best. Moreover, the retained austenite grains rotated significantly in the early stage of the specimen deformation process (around yielding), and the work hardening of the specimen was weak at this stage, simultaneously. Full article
(This article belongs to the Special Issue Microstructure and Mechanical Properties Relationship for Metallic Materials)
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18 pages, 8443 KiB  
Article
Local Mechanical Properties and Microstructure of EN AW 6082 Aluminium Alloy Processed via ECAP–Conform Technique
by Radek Procházka, Peter Sláma, Jaromír Dlouhý, Pavel Konopík and Zuzanka Trojanová
Materials 2020, 13(11), 2572; https://0-doi-org.brum.beds.ac.uk/10.3390/ma13112572 - 05 Jun 2020
Cited by 8 | Viewed by 2531
Abstract
An ultrafine-grained EN AW 6082 aluminum alloy was prepared by continuous serve plastic deformation (i.e., thermo-mechanical equal channel angular pressing (ECAP)–Conform process). A miniaturized tensile testing technique was used for estimating local mechanical properties with the aim to reveal the inhomogeneity of elastic [...] Read more.
An ultrafine-grained EN AW 6082 aluminum alloy was prepared by continuous serve plastic deformation (i.e., thermo-mechanical equal channel angular pressing (ECAP)–Conform process). A miniaturized tensile testing technique was used for estimating local mechanical properties with the aim to reveal the inhomogeneity of elastic and plastic properties in a workpiece volume. These inhomogeneities may appear due to the irregular shear strain distribution in a Conformed wire. Miniaturized samples for tensile testing were cut from the Conformed workpiece. Elongation of miniaturized samples was measured with a 2D digital image correlation technique as the optical extensometer. Tensile test characteristics, such as the yield strength and ultimate tensile strength, were consequently compared with results of conventional and hardness tests. The microstructure of Conformed bars was studied in the cross-section perpendicular and parallel to the extrusion direction using scanning electron microscope (SEM) and electron backscatter diffraction (EBSD) analysis. The microstructure of samples exhibits pronounced inhomogeneity, which is reflected by the hardness and tensile test results. Estimated distinctions between peripheral and central parts of the Conformed wires are probably a consequence of the significant strain differences realized in the upper and bottom wire parts. Full article
(This article belongs to the Special Issue Microstructure and Mechanical Properties Relationship for Metallic Materials)
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