Editorial

3 pages, 401 KiB

Open AccessEditorial

New Frontiers in Materials Design for Laser Additive Manufacturing

by Silja-Katharina Rittinghaus, Eric A. Jägle, Manfred Schmid and Bilal Gökce

Materials 2022, 15(17), 6172; https://0-doi-org.brum.beds.ac.uk/10.3390/ma15176172 - 05 Sep 2022

Cited by 4 | Viewed by 1656

Laser-based additive manufacturing (LAM) in all its variations is now being established as a technique for manufacturing components from various material types and alloys [...] Full article

(This article belongs to the Special Issue New Frontiers in Materials Design for Laser Additive Manufacturing)

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Research

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11 pages, 2595 KiB

Open AccessArticle

Correlation between Differential Fast Scanning Calorimetry and Additive Manufacturing Results of Aluminium Alloys

by Olaf Kessler, Evgeny Zhuravlev, Sigurd Wenner, Steffen Heiland and Mirko Schaper

Materials 2022, 15(20), 7195; https://0-doi-org.brum.beds.ac.uk/10.3390/ma15207195 - 15 Oct 2022

Cited by 1 | Viewed by 970

Abstract

High-strength aluminium alloy powders modified with different nanoparticles by ball milling (7075/TiC, 2024/CaB6, 6061/YSZ) have been investigated in-situ during rapid solidification by differential fast scanning calorimetry (DFSC). Solidification undercooling has been evaluated and was found to decrease with an increasing number of nanoparticles, [...] Read more.

High-strength aluminium alloy powders modified with different nanoparticles by ball milling (7075/TiC, 2024/CaB6, 6061/YSZ) have been investigated in-situ during rapid solidification by differential fast scanning calorimetry (DFSC). Solidification undercooling has been evaluated and was found to decrease with an increasing number of nanoparticles, as the particles act as nuclei for solidification. Lower solidification undercooling of individual powder particles correlates with less hot cracking and smaller grains in the material produced by powder bed fusion of metals by a laser beam (PBF-LB/M). Quantitatively, solidification undercooling less than about 10–15 K correlates with almost crack-free PBF-LB/M components and grain sizes less than about 3 µm. This correlation shall be used for future purposeful powder material design on small quantities before performing extensive PBF-LB/M studies. Full article

(This article belongs to the Special Issue New Frontiers in Materials Design for Laser Additive Manufacturing)

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11 pages, 6096 KiB

Open AccessArticle

Microstructural Variations in Laser Powder Bed Fused Al–15%Fe Alloy at Intermediate Temperatures

by Wenyuan Wang, Naoki Takata, Asuka Suzuki, Makoto Kobashi and Masaki Kato

Materials 2022, 15(13), 4497; https://0-doi-org.brum.beds.ac.uk/10.3390/ma15134497 - 26 Jun 2022

Cited by 4 | Viewed by 1434

Abstract

The samples of the Al–15Fe (mass%) binary alloy that were additively manufactured by laser powder bed fusion (L-PBF) were exposed to intermediate temperatures (300 and 500 °C), and the thermally induced variations in their microstructural characteristics were investigated. The L-PBF-manufactured sample was found [...] Read more.

The samples of the Al–15Fe (mass%) binary alloy that were additively manufactured by laser powder bed fusion (L-PBF) were exposed to intermediate temperatures (300 and 500 °C), and the thermally induced variations in their microstructural characteristics were investigated. The L-PBF-manufactured sample was found to have a microstructure comprising a stable θ-Al₁₃Fe₄ phase localized around melt-pool boundaries and several spherical metastable Al₆Fe-phase particles surrounded by a nanoscale α-Al/Al₆Fe cellular structure in the melt pools. The morphology of the θ phase remained almost unchanged even after 1000 h of exposure at 300 °C. Moreover, the nanoscale α-Al/Al₆Fe cellular structure dissolved in the α-Al matrix; this was followed by the growth (and nucleation) of the spherical Al₆Fe-phase particles and the precipitation of the θ phase. Numerous equiaxed grains were formed in the α-Al matrix during the thermal exposure, which led to the formation of a relatively homogenous microstructure. The variations in these microstructural characteristics were more pronounced at the higher investigated temperature of 500 °C. Full article

(This article belongs to the Special Issue New Frontiers in Materials Design for Laser Additive Manufacturing)

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22 pages, 8321 KiB

Open AccessArticle

Quality over Quantity: How Different Dispersion Qualities of Minute Amounts of Nano-Additives Affect Material Properties in Powder Bed Fusion of Polyamide 12

by Alexander Sommereyns, Stan Gann, Jochen Schmidt, Abootorab Baqerzadeh Chehreh, Arne Lüddecke, Frank Walther, Bilal Gökce, Stephan Barcikowski and Michael Schmidt

Materials 2021, 14(18), 5322; https://0-doi-org.brum.beds.ac.uk/10.3390/ma14185322 - 15 Sep 2021

Cited by 4 | Viewed by 2271

Abstract

The great interest, within the fields of research and industry, in enhancing the range and functionality of polymer powders for laser powder bed fusion (LB-PBF-P) increases the need for material modifications. To exploit the full potential of the additivation method of feedstock powders [...] Read more.

The great interest, within the fields of research and industry, in enhancing the range and functionality of polymer powders for laser powder bed fusion (LB-PBF-P) increases the need for material modifications. To exploit the full potential of the additivation method of feedstock powders with nanoparticles, the influence of nanoparticles on the LB-PBF process and the material behavior must be understood. In this study, the impact of the quantity and dispersion quality of carbon nanoparticles deposited on polyamide 12 particles is investigated using tensile and cubic specimens manufactured under the same process conditions. The nano-additives are added through dry coating and colloidal deposition. The specimens are analyzed by tensile testing, differential scanning calorimetry, polarized light and electron microscopy, X-ray diffraction, infrared spectroscopy, and micro-computed tomography. The results show that minute amounts (0.005 vol%) of highly dispersed carbon nanoparticles shift the mechanical properties to higher ductility at the expense of tensile strength. Despite changes in crystallinity due to nano-additives, the crystalline phases of polyamide 12 are retained. Layer bonding and part densities strongly depend on the quantity and dispersion quality of the nanoparticles. Nanoparticle loadings for CO₂ laser-operated PBF show only minor changes in material properties, while the potential is greater at lower laser wavelengths. Full article

(This article belongs to the Special Issue New Frontiers in Materials Design for Laser Additive Manufacturing)

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11 pages, 5347 KiB

Open AccessArticle

Physical and Geometrical Properties of Additively Manufactured Pure Copper Samples Using a Green Laser Source

by Samira Gruber, Lukas Stepien, Elena López, Frank Brueckner and Christoph Leyens

Materials 2021, 14(13), 3642; https://0-doi-org.brum.beds.ac.uk/10.3390/ma14133642 - 29 Jun 2021

Cited by 30 | Viewed by 2314

Abstract

So far, copper has been difficult to process via laser powder bed fusion due to low absorption with the frequently used laser systems in the infrared wavelength range. However, green laser systems have emerged recently and offer new opportunities in processing highly reflective [...] Read more.

So far, copper has been difficult to process via laser powder bed fusion due to low absorption with the frequently used laser systems in the infrared wavelength range. However, green laser systems have emerged recently and offer new opportunities in processing highly reflective materials like pure copper through higher absorptivity. In this study, pure copper powders from two suppliers were tested using the same machine parameter sets to investigate the influence of the powder properties on the material properties such as density, microstructure, and electrical conductivity. Samples of different wall thicknesses were investigated with the eddy-current method to analyze the influence of the sample thickness and surface quality on the measured electrical conductivity. The mechanical properties in three building directions were investigated and the geometrical accuracy of selected geometrical features was analyzed using a benchmark geometry. It could be shown that the generated parts have a relative density of above 99.95% and an electrical conductivity as high as 100% International Annealed Copper Standard (IACS) for both powders could be achieved. Furthermore, the negative influence of a rough surface on the measured eddy-current method was confirmed. Full article

(This article belongs to the Special Issue New Frontiers in Materials Design for Laser Additive Manufacturing)

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22 pages, 6458 KiB

Open AccessArticle

Improved Process Efficiency in Laser-Based Powder Bed Fusion of Nanoparticle Coated Maraging Tool Steel Powder

by Oliver Pannitz, Felix Großwendt, Arne Lüddecke, Arno Kwade, Arne Röttger and Jan Torsten Sehrt

Materials 2021, 14(13), 3465; https://0-doi-org.brum.beds.ac.uk/10.3390/ma14133465 - 22 Jun 2021

Cited by 8 | Viewed by 2114

Abstract

Research and development in the field of metal-based additive manufacturing are advancing steadily every year. In order to increase the efficiency of powder bed fusion of metals using a laser beam system (PBF LB/M), machine manufacturers have implemented extensive optimizations with regard to [...] Read more.

Research and development in the field of metal-based additive manufacturing are advancing steadily every year. In order to increase the efficiency of powder bed fusion of metals using a laser beam system (PBF LB/M), machine manufacturers have implemented extensive optimizations with regard to the laser systems and build volumes. However, the optimization of metallic powder materials using nanoparticle additives enables an additional improvement of the laser–material interaction. In this work, tool steel 1.2709 powder was coated with silicon carbide (SiC), few-layer graphene (FLG), and iron oxide black (IOB) on a nanometer scale. Subsequently, the feedstock material and the modified powder materials were analyzed concerning the reflectance of the laser radiation and processed by PBF-LB/M in a systematic and consistent procedure to evaluate the impact of the nano-additivation on the process efficiency and mechanical properties. As a result, an increased build rate is achieved, exhibiting a relative density of 99.9% for FLG/1.2709 due to a decreased reflectance of this modified powder material. Furthermore, FLG/1.2709 provides hardness values after precipitation hardening with only aging comparable to the original 1.2709 material and is higher than the SiC- and IOB-coated material. Additionally, the IOB coating tends to promote oxide-formation and lack-of-fusion defects. Full article

(This article belongs to the Special Issue New Frontiers in Materials Design for Laser Additive Manufacturing)

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24 pages, 8070 KiB

Open AccessArticle

Nanoparticle Tracing during Laser Powder Bed Fusion of Oxide Dispersion Strengthened Steels

by Yangyiwei Yang, Carlos Doñate-Buendía, Timileyin David Oyedeji, Bilal Gökce and Bai-Xiang Xu

Materials 2021, 14(13), 3463; https://0-doi-org.brum.beds.ac.uk/10.3390/ma14133463 - 22 Jun 2021

Cited by 14 | Viewed by 3120

Abstract

The control of nanoparticle agglomeration during the fabrication of oxide dispersion strengthened steels is a key factor in maximizing their mechanical and high temperature reinforcement properties. However, the characterization of the nanoparticle evolution during processing represents a challenge due to the lack of [...] Read more.

The control of nanoparticle agglomeration during the fabrication of oxide dispersion strengthened steels is a key factor in maximizing their mechanical and high temperature reinforcement properties. However, the characterization of the nanoparticle evolution during processing represents a challenge due to the lack of experimental methodologies that allow in situ evaluation during laser powder bed fusion (LPBF) of nanoparticle-additivated steel powders. To address this problem, a simulation scheme is proposed to trace the drift and the interactions of the nanoparticles in the melt pool by joint heat-melt-microstructure–coupled phase-field simulation with nanoparticle kinematics. Van der Waals attraction and electrostatic repulsion with screened-Coulomb potential are explicitly employed to model the interactions with assumptions made based on reported experimental evidence. Numerical simulations have been conducted for LPBF of oxide nanoparticle-additivated PM2000 powder considering various factors, including the nanoparticle composition and size distribution. The obtained results provide a statistical and graphical demonstration of the temporal and spatial variations of the traced nanoparticles, showing ∼55% of the nanoparticles within the generated grains, and a smaller fraction of ∼30% in the pores, ∼13% on the surface, and ∼2% on the grain boundaries. To prove the methodology and compare it with experimental observations, the simulations are performed for LPBF of a 0.005 wt % yttrium oxide nanoparticle-additivated PM2000 powder and the final degree of nanoparticle agglomeration and distribution are analyzed with respect to a series of geometric and material parameters. Full article

(This article belongs to the Special Issue New Frontiers in Materials Design for Laser Additive Manufacturing)

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18 pages, 5608 KiB

Open AccessArticle

Development of a Laser Powder Bed Fusion Process Tailored for the Additive Manufacturing of High-Quality Components Made of the Commercial Magnesium Alloy WE43

by Stefan Julmi, Arvid Abel, Niklas Gerdes, Christian Hoff, Jörg Hermsdorf, Ludger Overmeyer, Christian Klose and Hans Jürgen Maier

Materials 2021, 14(4), 887; https://0-doi-org.brum.beds.ac.uk/10.3390/ma14040887 - 13 Feb 2021

Cited by 15 | Viewed by 2749

Abstract

Additive manufacturing (AM) has become increasingly important over the last decade and the quality of the products generated with AM technology has strongly improved. The most common metals that are processed by AM techniques are steel, titanium (Ti) or aluminum (Al) alloys. However, [...] Read more.

Additive manufacturing (AM) has become increasingly important over the last decade and the quality of the products generated with AM technology has strongly improved. The most common metals that are processed by AM techniques are steel, titanium (Ti) or aluminum (Al) alloys. However, the proportion of magnesium (Mg) in AM is still negligible, possibly due to the poor processability of Mg in comparison to other metals. Mg parts are usually produced by various casting processes and the experiences in additive manufacturing of Mg are still limited. To address this issue, a parameter screening was conducted in the present study with experiments designed to find the most influential process parameters. In a second step, these parameters were optimized in order to fabricate parts with the highest relative density. This experiment led to processing parameters with which specimens with relative densities above 99.9% could be created. These high-density specimens were then utilized in the fabrication of test pieces with several different geometries, in order to compare the material properties resulting from both the casting process and the powder bed fusion (PBF-LB) process. In this comparison, the compositions of the occurring phases and the alloys’ microstructures as well as the mechanical properties were investigated. Typically, the microstructure of metal parts, produced by PBF-LB, consisted of much finer grains compared to as-cast parts. Consequently, the strength of Mg parts generated by PBF-LB could be further increased. Full article

(This article belongs to the Special Issue New Frontiers in Materials Design for Laser Additive Manufacturing)

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