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A special issue of Crystals (ISSN 2073-4352). This special issue belongs to the section "Inorganic Crystalline Materials".

Deadline for manuscript submissions: closed (25 December 2023) | Viewed by 13771

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Dr. Subbarayan Sivasankaran

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Department of Mechanical Engineering, Qassim University, Buraydah, Saudi Arabia
Interests: additive manufacturing; mechanical behavior; nanocomposites; mechanical alloying; powder metallurgy; liquid metallurgy; advanced welding; high entropy alloys, biodegradable alloys, thermoelectric materials, oxide dispersion strengthening alloys, high temperature forming, metal matrix composites; polymer matrix composites; advanced characterization techniques; optimization and modeling, advanced materials design
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Dear Colleagues,

We are pleased to announce the Special Issue entitled “Microstructure and Mechanical Properties of Alloys” is devoted to cover the mechanical behavior of advanced engineering materials. The main aims of this Special Issue are to collect the original state-of-the art research works, technical research articles, and or comprehensive review articles in the field of structural metals/alloys includes metal matrix composites, nanostructured materials, high-entropy alloys, bulk-metallic glasses, and oxide dispersion strengthened alloys. The works demonstrating alloys with tensile, compression, shear, torsion, creep, and fatigue behavior from the elastic to plastic stage are focused through this Special Issue. This Special Issue encourages the researchers for describing the mechanical behavior by correlating several characterization techniques, namely, X-ray diffraction, optical microscope, scanning electron microscope, transmission electron microscope, and atomic probe tomography. The advanced materials manufactured from powder metallurgy, casting, laser processing, thin film technology, additive printing technology, etc., are the main scope of this Special Issue. Further, material modeling, finite element analysis, and any modelling techniques (using artificial intelligent) dealing with the mechanical behavior of alloys are also covered in this Special Issue. Original full length articles, short communications, and review articles are subjected to be peer review by eminent researchers working in this field.

With immense pleasure, we invite the authors to submit their original scientific contributions to this Special Issue.

Dr. Subbarayan Sivasankaran
Guest Editor

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Manuscripts should be submitted online at www.mdpi.com by registering and logging in to this website. Once you are registered, click here to go to the submission form. Manuscripts can be submitted until the deadline. All submissions that pass pre-check are peer-reviewed. Accepted papers will be published continuously in the journal (as soon as accepted) and will be listed together on the special issue website. Research articles, review articles as well as short communications are invited. For planned papers, a title and short abstract (about 100 words) can be sent to the Editorial Office for announcement on this website.

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. Crystals is an international peer-reviewed open access monthly 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

microstructural characterization
metals/alloys
metal matrix composites
mechanical strength
stress–strain
constitutive modeling
metal forming
fractography
workability
forming
casting
powder metallurgy
welding
3D printing
laser processing

Published Papers (13 papers)

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Research

23 pages, 10699 KiB

Open AccessArticle

Influence of Processing Temperature and Strain Rate on the Microstructure and Mechanical Properties of Magnesium Alloys Processed by Single-Pass Differential Speed Rolling

by Christopher Hale, Zhigang Xu, Svitlana Fialkova, Jessica Rawles and Jagannathan Sankar

Crystals 2024, 14(3), 262; https://0-doi-org.brum.beds.ac.uk/10.3390/cryst14030262 - 6 Mar 2024

Viewed by 827

Abstract

Magnesium-based alloys show significant promise for widespread applications owing to their lightweight nature and improved mechanical properties achieved through grain refinement via hot rolling. This investigation focuses on Mg-xAl-yCa-zMn (AXM alloys), pre-heated to temperatures of 350, 400, and 450 °C and processed via both single-pass differential speed rolling (DSR) and conventional rolling (CR). The key findings reveal the interplay between processing temperature, strain rate during single-pass rolling, and an innovative approach for incorporating varying amounts of Ca, influencing grain size, quantity of dynamic recrystallization (DRX) grains, and overall mechanical properties, including strength and ductility. A noteworthy observation is the positive correlation between an increase in the total reduction during hot rolling and a higher fraction of DRXed grains. This leads to a significant reduction in average grain size, diminishing from 60.3 ± 54.3 μm to 19.5 ± 14.2 μm at 40%, nearly a third the size of T4 grains (the initial homogenized microstructure of the AXM alloys). The resultant material strength experiences a doubling from an average of 125 ± 10.2 MPa (T4) to 260 ± 25.8 MPa (DSR rolled at 40%) for the AXM alloys with potential improvement in the ductility depending on rolling speed conditions. This study also aims to analyze the combination of rolling temperature, rolling speed, thickness reduction, speed difference and Ca content implemented across a wide range of temperatures and strain rates to provide a holistic approach to the processing parameters affecting the microstructure and mechanical properties of AXM alloys. Furthermore, this study provides a deeper understanding of DRX mechanisms, including continuous DRX (CDRX), discontinuous DRX (DDRX), and twinning induced DRX (TDRX), while each of these mechanisms plays a distinct role in the overall enhancement of formability and performance of magnesium alloys. Full article

(This article belongs to the Special Issue Micro-Structure and Mechanical Properties of Alloys)

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14 pages, 4233 KiB

Open AccessArticle

Enhancement of Creep Lifetime of Aluminum through Severe Plastic Deformation

by Petr Král, Jiří Dvořák, Marie Kvapilová, Andrej G. Kadomtsev and Václav Sklenička

Crystals 2024, 14(3), 230; https://0-doi-org.brum.beds.ac.uk/10.3390/cryst14030230 - 28 Feb 2024

Viewed by 681

Abstract

This work investigates the creep behavior of severely deformed commercial aluminum. The commercial aluminum was processed by helical rolling (HR) and equal-channel angular pressing (ECAP) at room temperature. During these processes, the equivalent strain up to about 4 was imposed into the as-received material. The creep testing at 200 °C revealed that HR and ECAP significantly increased the time to fracture compared to the as-received material. The stress dependences showed that the value of stress exponent n decreased with the value of the imposed strain. The stress-change tests showed that as-received and severely deformed states exhibited different recovery rates after unloading. The microstructure analysis showed that creep behavior was influenced by the microstructure formed during severe plastic deformation. The relationships between creep behavior and microstructure in the investigated states are discussed. Full article

(This article belongs to the Special Issue Micro-Structure and Mechanical Properties of Alloys)

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18 pages, 7573 KiB

Open AccessArticle

Effect of Nickel Addition on Solidification Microstructure and Tensile Properties of Cast 7075 Aluminum Alloy

by Kai Wang, Haoran Qi, Simu Ma, Linrui Wang, Naijun He and Fuguo Li

Crystals 2023, 13(11), 1589; https://0-doi-org.brum.beds.ac.uk/10.3390/cryst13111589 - 17 Nov 2023

Viewed by 898

Abstract

In order to explore the casting technology of a high–strength aluminum alloy, the effects of nickel on the solidified microstructure and tensile properties of a 7075 aluminum alloy were studied. 7075 aluminum alloys without nickel and with 0.6% and 1.2% nickel were prepared by a casting method. The results showed that the increase of Ni content in the 7075 alloys increased the liquidus temperatures, primary α (Al) grains were refined significantly, and the divorced eutectic structure was gradually formed among α (Al) grains with the preformation of the Al₃Ni phase. In comparison, the 7075 alloy with 0.6% nickel content had less intergranular shrinkage porosity, and its elongation and ultimate tensile strength was enhanced 45% and 105% higher than those of the as-cast 7075 aluminum alloy, respectively. When the Ni content was increased to 1.2%, the eutectic phases of the alloy became much coarser compared to the other two alloys, and the mechanical properties obviously reduced too. Full article

(This article belongs to the Special Issue Micro-Structure and Mechanical Properties of Alloys)

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11 pages, 1670 KiB

Open AccessArticle

Effects of Uniaxial Tensile Strain on Mechanical Properties of Al₆MgNb: A First-Principles Study

by Lihua Zhang, Jijun Li, Jing Zhang, Yanjie Liu and Lin Lin

Crystals 2023, 13(10), 1458; https://0-doi-org.brum.beds.ac.uk/10.3390/cryst13101458 - 2 Oct 2023

Viewed by 655

Abstract

The effects of uniaxial tensile strain in the x direction (ε_x) on the mechanical properties of the Al₆MgNb compound were explored by carrying out first-principles calculations based on the density functional theory (DFT). The calculation results showed that the Al₆MgNb compound was stable in mechanics at a uniaxial tensile strain range of 0–12%. The shear modulus G, bulk modulus B and Young’s modulus E of the Al₆MgNb compound all decreased as the uniaxial tensile strain ε_x grew from 0 to 12%, exhibiting the negative sensitivities of elastic moduli to uniaxial tensile strain. The Poisson ratio ν of the Al₆MgNb compound grew with the increase in uniaxial tensile strain ε_x from 0 to 7%, exhibiting the positive sensitivity of Poisson’s ratio to uniaxial tensile strain, but it decreased as the uniaxial tensile strain ε_x increased from 7% to 12%, exhibiting its negative sensitivity to the uniaxial tensile strain. The Al₆MgNb compound possesses the optimal toughness under a uniaxial tensile strain ε_x of 7% because of the largest value of ν. The Vickers hardness H_V of the Al₆MgNb compound decreased first and then remained stable with the growth in uniaxial tensile strain ε_x from 0 to 12%, exhibiting the significant negative sensitivity of the Vickers hardness to tensile uniaxial strain at a strain range of 0–7%. The ratio of the bulk modulus B to the elastic shear modulus G (i.e., B/G) increased first and then decreased with the growth in uniaxial tensile strain ε_x from 0 to 12%. The highest ductility is achieved for the Al₆MgNb compound at a strain ε_x of 7% because of the largest value of B/G. The compression anisotropy percentage A_B, shear anisotropy percentage A_G and the universal anisotropy index A_U of the Al₆MgNb compound all increased as the uniaxial tensile strain ε_x increased from 0 to 12%, exhibiting the positive sensitivity of elastic anisotropy to the uniaxial tensile strain. Our study suggested that the mechanical properties of the Al₆MgNb compound can be influenced and regulated by applying proper uniaxial tensile strain. These findings can provide a favorable reference to the study on mechanical performance of Al-Mg-based materials by means of strain modulation. Full article

(This article belongs to the Special Issue Micro-Structure and Mechanical Properties of Alloys)

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13 pages, 5919 KiB

Open AccessArticle

Effect of Graphene on the Microstructure and Mechanical Properties of WC-Based Cemented Carbide

by Wanzhen Qi, Zhiwei Zhao, Yanju Qian, Shijie Zhang, Hongjuan Zheng, Xiaomiao Zhao, Xinpo Lu and Shun Wang

Crystals 2023, 13(10), 1414; https://0-doi-org.brum.beds.ac.uk/10.3390/cryst13101414 - 23 Sep 2023

Cited by 1 | Viewed by 652

Abstract

WC-based cemented carbides were prepared by spark plasma sintering (SPS) of WC-Co-Cr₃C₂-VC alloy powder by adding different contents of graphene. The phase composition, microstructure, mechanical properties, and magnetic properties of cemented carbide were investigated by means of XRD, SEM, Vickers hardness and fracture toughness tests, and magnetic properties tests. The results showed that the mechanical properties of the specimens show a trend of first increasing and then decreasing with the increase in graphene content. After adding 0.6 wt.% graphene, graphene is uniformly distributed on the substrate in the form of flakes, WC grain size decreases, the hardness of the specimen increases to 2009 HV, the relative density increases to 94.3%, the fracture toughness is 11.72 MPa·m^1/2, and the coercivity of the sample is 437.55 Oe. Therefore, cemented carbide with a graphene content of 0.6 wt.% has excellent comprehensive performance (Vickers hardness and fracture toughness). Full article

(This article belongs to the Special Issue Micro-Structure and Mechanical Properties of Alloys)

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13 pages, 21866 KiB

Open AccessArticle

Effect of Mischmetal Addition on Microstructure and Mechanical Properties of As-Cast and As-Rolled Mg–Sn–Ca Alloys

by Jun Luo, Lijun Dong, Guowei Zhong, Zhenxing Duan, Shuang Chen and Anru Wu

Crystals 2023, 13(9), 1379; https://0-doi-org.brum.beds.ac.uk/10.3390/cryst13091379 - 17 Sep 2023

Viewed by 671

Abstract

The microstructures and mechanical properties of Mg–3Sn–0.1Ca–xMM (mischmetal, x = 0.3, 0.6, and 0.9 wt.%) alloys were investigated. Optical microscopy (OM), scanning electron microscopy (SEM) and X-ray diffraction spectroscopy (XRD) were used to characterize the microstructures and phase constitutions of the cast and rolled alloys. Room temperature tensile tests were conducted to obtain the mechanical properties and macro-textures to evaluate the texture weakening effect results of the MM. The results show that an abundance of second phase formed, confirmed as the (Ca,MM)MgSn phase, and the volume fraction increased with the increasing MM addition. The tensile yield strength of the as-cast alloys increased with the MM addition, but the elongation decreased. All of the rolled Mg–3Sn–0.1Ca–xMM alloys showed a strong basal texture, and only slightly decreased in intensity after annealing treatment due to the particle-stimulated nucleation of recrystallization. The as-annealed Mg–3Sn–0.1Ca–0.6MM alloys exhibited the highest tensile strengths of 266.5 ± 3.3 MPa and 136.1 ± 3.7 MPa, which are mainly ascribed to grain refinement strengthening, Orowan strengthening and texture strengthening. Full article

(This article belongs to the Special Issue Micro-Structure and Mechanical Properties of Alloys)

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13 pages, 24834 KiB

Open AccessArticle

Influence of a Novel Double Tempering Process on the Microstructure and Mechanical Properties of Cu-Alloyed Austempered Ductile Iron with Possible Nano (Micro)-Characterization Using Neutron Beam Techniques

by Nikša Čatipović, Massimo Rogante, Hasan Avdušinović and Karla Grgić

Crystals 2023, 13(9), 1359; https://0-doi-org.brum.beds.ac.uk/10.3390/cryst13091359 - 8 Sep 2023

Viewed by 665

Abstract

In this paper, a novel method for the double heat treatment of ductile iron was applied. Ten sets of specimens (three specimens in each set) of ductile cast iron (DCI) containing 0.51% wt. Cu were prepared and converted to austenitic ductile iron. All specimens were austenitized at 850 °C for 60 min and annealed at 420 °C, 331 °C and 250 °C for 120, 68 and 30 min, respectively. Five sets of samples were then annealed at 500 °C for 60 min, creating a novel double heat treatment process for annealing. Finally, all specimens were slowly cooled in air at ambient temperature. Tensile strength, hardness and elongation were measured in all specimens to compare the specimens with and without subsequent tempering. A microstructural analysis was also performed, which showed that the microstructure changed for the specimens that were subsequently tempered with. The results show that specimens with subsequent tempering have slightly higher hardness, a small decrease in tensile strength and significantly higher elongation. In addition, specimens with subsequent tempering exhibit more uniform mechanical properties compared to specimens without subsequent tempering. The use of neutron beam techniques was proposed to further characterize the newly formed microstructure after subsequent tempering. Full article

(This article belongs to the Special Issue Micro-Structure and Mechanical Properties of Alloys)

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16 pages, 4707 KiB

Open AccessArticle

Mechanical Characterization and Microstructural Analysis of Stir-Cast Aluminum Matrix Composites (LM5/ZrO₂)

by Jayavelu Udaya Prakash, Sunder Jebarose Juliyana, Sachin Salunkhe, Sharad Ramdas Gawade, Emad S. Abouel Nasr and Ali K. Kamrani

Crystals 2023, 13(8), 1220; https://0-doi-org.brum.beds.ac.uk/10.3390/cryst13081220 - 7 Aug 2023

Cited by 3 | Viewed by 1031

Abstract

Aluminum matrix composites (AMCs) are largely used in defense, maritime, and space applications for their excellent properties. LM5 is used where very high resistance to corrosion from seawater or marine atmospheres is required, for equipment used for the manufacture of foodstuffs, cooking utensils, and chemical plants. Zirconia is preferred over other reinforcements as it shows comparatively great refractory properties, high scratch resistance, and thermal shock resistance. Utilizing the stir casting technique, an attempt was made to produce AMCs of LM5 aluminum alloy strengthened with ZrO₂. The weight percentage of ZrO₂ was changed to 0%, 3%, 6%, and 9%. The specimens were prepared and tested as per ASTM standards to find the density, micro and macro hardness, impact, tensile, and compressive strength. The micrographs and SEM images confirm the uniform distribution of ZrO₂ particles in the aluminum matrix. LM5/9%ZrO₂ AMC has the highest density value of 2.83 g/cm³ and LM5/3%ZrO₂ has the least porosity of 2.55%. LM5/9% ZrO₂ has the highest hardness values of 78 VHN and 72 HRE. LM5/6% ZrO₂ AMC has the highest tensile strength of 220 MPa, compressive strength of 296 MPa, and toughness of 12 J. LM5/6% ZrO₂ AMCs may be used for many structural applications. Full article

(This article belongs to the Special Issue Micro-Structure and Mechanical Properties of Alloys)

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13 pages, 3179 KiB

Open AccessArticle

Evaluation of Retained Austenite in Carburized Bearing Steel Using Magneto-Inductive Method

by Laura G. Ionescu, Mangesh V. Pantawane, Constantin Tănase, Răducu V. Sichim, Catalina A. Dascălu and Brânduşa Ghiban

Crystals 2023, 13(8), 1173; https://0-doi-org.brum.beds.ac.uk/10.3390/cryst13081173 - 28 Jul 2023

Viewed by 834

Abstract

The present work explores the magneto-inductive method to evaluate different levels of retained austenite content in carburized 20NiCrMo7 bearing steel while comparing the corresponding measurements by X-ray diffractometry and image analysis by optical microscope. The content of retained austenite in carburized 20NiCrMo7 steel was modified with additional tempering to yield three samples with distinct ranges of retained austenite profiles in the carburized region of the steel. The retained austenite measured at different depths in these samples using the magneto-inductive method had an outcome comparable to other methods. Further discussion based on data suggests that the magneto–induction method yields precise (with an average deviation of 0.5%) results with sufficient sensitivity at different levels (including below 5 vol. %.) of retained austenite. Full article

(This article belongs to the Special Issue Micro-Structure and Mechanical Properties of Alloys)

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17 pages, 6866 KiB

Open AccessArticle

Phase Composition and Temperature Effect on the Dynamic Young’s Modulus, Shear Modulus, Internal Friction, and Dilatometric Changes in AISI 4130 Steel

by Lioudmila A. Matlakhova, Emanuel C. Pessanha, Henrique Alves, Natalia A. Palii and Sergio N. Monteiro

Crystals 2023, 13(6), 930; https://0-doi-org.brum.beds.ac.uk/10.3390/cryst13060930 - 9 Jun 2023

Viewed by 1528

Abstract

Elastic properties of materials and their changes with temperature are important for their applications in engineering. In the present study the influence of phase composition and temperature of AISI 4130 alloy on Young’s modulus (E_d), shear modulus (G_d), and damping (Q⁻¹) was carried out by the impulse excitation technique (IET). The material characterization was performed using confocal microscopy, XRD, SEM, HV, and dilatometry. A stable structure, composed of ferrite (BCC) and pearlite (α-Fe + Fe₃C), was obtained by annealing. Metastable structure of martensite (BCT) was obtained by quenching. The E_d, G_d, and Q⁻¹ were measured by varying the temperature from RT to 900 °C. The values of E_d and G_d, at RT, were determined as 201.5 and 79.2 GPa (annealed) and 190.13 and 76.5 GPa (quenched), respectively. In the annealed steel, the values E_d and G_d decrease linearly on heating up to 650 °C, with thermal expansion. In the quenched steel, weak changes occurred in the dilatometric curve, E_d, G_d, and Q⁻¹, in the range of 350–450 °C, which indicated decompositions of the martensitic phase. A sharp decrease in the moduli and high peak of Q⁻¹ were observed for both samples around 650–900 °C, revealing low lattice elastic stability of the phases during transformations α(BCC) + Fe₃Cγ(FCC). Full article

(This article belongs to the Special Issue Micro-Structure and Mechanical Properties of Alloys)

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24 pages, 19962 KiB

Open AccessArticle

Influence of Oxide Dispersions (Al₂O₃, TiO₂, and Y₂O₃) in CrFeCuMnNi High-Entropy Alloy on Microstructural Changes and Corrosion Resistance

by Subbarayan Sivasankaran, El-Sayed M. Sherif, Hany R. Ammar, Abdulaziz S. Alaboodi and Abdel-baset H. Mekky

Crystals 2023, 13(4), 605; https://0-doi-org.brum.beds.ac.uk/10.3390/cryst13040605 - 1 Apr 2023

Cited by 5 | Viewed by 1451

Abstract

This study investigates the influence of 3 vol.% Al₂O₃, 3 vol.% TiO₂, and 3 vol.% Y₂O₃ in the CrFeCuMnNi equimolar high-entropy alloy on its microstructural changes and corrosion resistance. These oxide-dispersed high-entropy composites (ODS-HECs) were synthesized via high-energy ball milling (50 h) followed by uniaxial hot-compaction (550 MPa, 45 min), medium-frequency sintering (1100 °C, 20 min), and hot forging (50 MPa). The microstructures of the developed composites produced a stable FCC phase, a small amount of ordered BCC-B2 structure, Fe₂O₃, and corresponding dispersed oxide phases. The corrosion of the developed high-entropy composites was tested in 3.5% NaCl solution using several electrochemical techniques. The results revealed that the corrosion rate (R_Corr) decreased with the incorporation of oxide particles. Among the investigated samples and based on the electrochemical impedance spectroscopy results, CrFeCuMnNi-3 vol.% TiO₂ ODS-HECs were seen to possess the highest value of corrosion resistance (R_P). The change in the chronoamperometric current with time indicated that the CrFeCuMnNi alloy suffered pitting corrosion which decreased when Al₂O₃ was added, forming a CrFeCuMnNi-3 vol.% Al₂O₃ sample. In contrast, the incorporation of a 3 vol.% Y₂O₃, and 3 vol. TiO₂, prevents pitting. Full article

(This article belongs to the Special Issue Micro-Structure and Mechanical Properties of Alloys)

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19 pages, 11090 KiB

Open AccessArticle

Influence of Milling Time and Ball-to-Powder Ratio on Mechanical Behavior of FeMn₃₀Cu₅ Biodegradable Alloys Prepared by Mechanical Alloying and Hot-Forging

by Subbarayan Sivasankaran, Hany R. Ammar, Bandar Almangour, Samir Ali Elborolosy, Abdel-baset H. Mekky and Abdulaziz S. Alaboodi

Crystals 2022, 12(12), 1777; https://0-doi-org.brum.beds.ac.uk/10.3390/cryst12121777 - 7 Dec 2022

Cited by 6 | Viewed by 1743

Abstract

FeMn₃₀Cu₅ is a biodegradable and multi-component alloy that can be used to repair bone defects in load-bearing parts in the medical field. This work focuses on studying the influence of milling time and ball-to-powder ratio (BPR) on the mechanical behavior of FeMn₃₀Cu₅ alloys via mechanical alloying and hot-forging. Three different milling times (1, 5.5, and 10 h) and BPRs (5:1, 10:1, and 15:1) were used as the main independent variables. MA was performed at 300 rpm in ethanol; the synthesized powders were dried, hot-compacted at 550 MPa, and sintered under an inert atmosphere (1000 °C, 15 min) using a medium-frequency induction furnace and hot-forging. The mechanical behavior in terms of Vickers hardness, compressive stress–strain curves, and percentage theoretical density was investigated. This experimental work revealed that both milling time and BPR significantly influenced the grain size reduction owing to variations in the severe plastic deformation and mechanical collisions produced by the milling medium. The hardness and ultimate strength of the FeMn₃₀Cu₅ alloy processed at 10 h and 15:1 BPR were 1788.17 ± 4.9 MPa, which was 1.5 times higher than those of the same alloy processed at 1 h and 5:1 BPR (1200.45 ± 6.5 MPa). Austenite iron (g-Fe), ferrite-iron (a-Fe), a-Mn, and a-Cu phases were observed in XRD and SEM images. The formed a-Mn and a-Cu overlapped with the g-Fe lattice because of the diffusion of Mn and Cu atoms during sintering and hot-forging. The incorporated 30 wt.% of Mn and 5 wt.% of Cu stabilize the austenite phase (good for MRI scans in medical applications), which contributed to promoting superior mechanical properties with milling time (10 h) and BPR (15:1) due to severe structural defects. Full article

(This article belongs to the Special Issue Micro-Structure and Mechanical Properties of Alloys)

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11 pages, 4390 KiB

Open AccessArticle

Achieving High Tensile Strength of Heat-Resistant Ni-Fe-Based Alloy by Controlling Microstructure Stability for Power Plant Application

by Fei Sun

Crystals 2022, 12(10), 1433; https://0-doi-org.brum.beds.ac.uk/10.3390/cryst12101433 - 11 Oct 2022

Viewed by 1313

Abstract

A new, wrought Ni-Fe-based alloy with excellent creep rupture life has been developed for 700 °C-class advanced ultra-supercritical (A-USC) steam turbine rotor application. In this study, its tensile deformation behaviors and related microstructure evolution were investigated. Tensile tests were carried out at room temperature, 700 °C, and 750 °C. The results show that the Ni-Fe-based alloy has excellent yield strength at 700 °C, which is higher than that of some other Ni-based/Ni-Fe-based alloys. The fracture surface characteristics indicate trans-granular and intergranular fracture modes at room temperature, 700 °C, and 750 °C. However, the intergranular fraction mode became dominant above 700 °C. Dynamic recrystallization occurred at 700 °C and 750 °C with increasing average misorientation angles. The volume fraction of the γ′ precipitate was around 20%, and the average size of the γ′ precipitates was around 30 μm, which had no noticeable change after the tensile tests. The predominant deformation mechanisms were planar slip at room temperature, bypassing of the γ′ precipitates by the Orowan mechanism, and dislocation shearing at 700 °C and 750 °C. The tensile properties, fracture characteristics, and deformation mechanisms have been well-correlated. The results are helpful in providing experimental evidence for the development and optimization of high-temperature alloys for 700 °C-class A-USC applications. Full article

(This article belongs to the Special Issue Micro-Structure and Mechanical Properties of Alloys)

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