Aluminum alloys, known for their high strength-to-weight ratios and impressive electrical and thermal conductivities, are extensively used in numerous engineering sectors, such as aerospace, automotive, and construction. Recently, significant efforts have been made to develop novel aluminum alloys specifically tailored for additive manufacturing. These new alloys aim to provide an optimal balance between mechanical properties and thermal/ electrical conductivities. In this study, nine combinatorial samples with various alloy compositions were fabricated using direct energy deposition (DED) additive manufacturing by adjusting the feeding speeds of Al6061 alloy and Al-12Si alloy powders. The effects of the alloying elements on the microstructure, electrical conductivity, and hardness were investigated. Generally, as the Si and Cu contents decreased, electrical conductivity increased and hardness decreased, exhibiting trade-off characteristics. However, electrical conductivity and hardness showed an optimal combination when the Si content was adjusted to below 4.5 wt%, which can sufficiently suppress the grain boundary segregation of the α- Si precipitates, and the Cu content was controlled to induce the formation of Al₂Cu precipitates.

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• Trends in Materials Modeling and Computation for Metal Additive Manufacturing
  Seoyeon Jeon, Hyunjoo Choi
  journal of Korean Powder Metallurgy Institute.2024; 31(3): 213.     CrossRef

Aluminum alloys are widely utilized in diverse industries, such as automobiles, aerospace, and architecture, owing to their high specific strength and resistance to oxidation. However, to meet the increasing demands of the industry, it is necessary to design new aluminum alloys with excellent properties. Thus, a new method is required to efficiently test additively manufactured aluminum alloys with various compositions within a short period during the alloy design process. In this study, a combinatory approach using a direct energy deposition system for metal 3D printing process with a dual feeder was employed. Two types of aluminum alloy powders, namely Al6061 and Al-12Cu, were utilized for the combinatory test conducted through 3D printing. Twelve types of Al-Si-Cu-Mg alloys were manufactured during this combinatory test, and the relationship between their microstructures and properties was investigated.

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• Combinatorial Experiment for Al-6061 and Al-12Si alloy Based on Directed Energy Deposition (DED) Process
  Seoyeon Jeon, Suwon Park, Yongwook Song, Jiwon Park, Hyunyoung Park, Boram Lee, Hyunjoo Choi
  journal of Korean Powder Metallurgy Institute.2023; 30(6): 463.     CrossRef

The Ag/WC electrical contacts were prepared via powder metallurgy using 60 wt% Ag, 40 wt% WC, and small amounts of Co₃O₄ with varying WC particle sizes. After the fabrication of the contact materials, microstructure observations confirmed that WC-1 had an average grain size (AGS) of 0.27 μm, and WC-2 had an AGS of 0.35 μm. The Ag matrix in WC-1 formed fine grains, whereas a significantly larger and continuous growth of the Ag matrix was observed in WC-2. This indicates the different flow behaviors of liquid Ag during the sintering process owing to the different WC sizes. The electrical conductivities of WC-1 and WC-2 were 47.8% and 60.4%, respectively, and had a significant influence on the Ag matrix. In particular, WC-2 exhibited extremely high electrical conductivity owing to its large and continuous Ag-grain matrix. The yield strengths of WC-1 and WC-2 after compression tests were 349.9 MPa and 280.7 MPa, respectively. The high yield strength of WC-1 can be attributed to the Hall–Petch effect, whereas the low yield strength of WC-2 can be explained by the high fraction of high-angle boundaries (HAB) between the WC grains. Furthermore, the relationships between the microstructure, electrical/mechanical properties, and deformation mechanisms were evaluated.

Metal additive manufacturing (AM) has transformed conventional manufacturing processes by offering unprecedented opportunities for design innovation, reduced lead times, and cost-effective production. Aluminum alloy, a material used in metal 3D printing, is a representative lightweight structural material known for its high specific strength and corrosion resistance. Consequently, there is an increasing demand for 3D printed aluminum alloy components across industries, including aerospace, transportation, and consumer goods. To meet this demand, research on alloys and process conditions that satisfy the specific requirement of each industry is necessary. However, 3D printing processes exhibit different behaviors of alloy elements owing to rapid thermal dynamics, making it challenging to predict the microstructure and properties. In this study, we gathered published data on the relationship between alloy composition, processing conditions, and properties. Furthermore, we conducted a sensitivity analysis on the effects of the process variables on the density and hardness of aluminum alloys used in additive manufacturing.

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• Effect of Heat Treatment on Microstructure and Mechanical Properties of Al–Zn–Mg–Cu–Si Sintered Alloys with and Without High-energy Ball Milling
  Junho Lee, Seonghyun Park, Sang-Hwa Lee, Seung Bae Son, Seok-Jae Lee, Jae-Gil Jung
  journal of Korean Powder Metallurgy Institute.2023; 30(6): 470.     CrossRef

Aluminum alloys are extensively employed in several industries, such as automobile, aerospace, and architecture, owing to their high specific strength and electrical and thermal conductivities. However, to meet the rising industrial demands, aluminum alloys must be designed with both excellent mechanical and thermal properties. Computer-aided alloy design is emerging as a technique for developing novel alloys to overcome these trade-off properties. Thus, the development of a new experimental method for designing alloys with high-throughput confirmation is gaining focus. A new approach that rapidly manufactures aluminum alloys with different compositions is required in the alloy design process. This study proposes a combined approach to rapidly investigate the relationship between the microstructure and properties of aluminum alloys using a direct energy deposition system with a dual-nozzle metal 3D printing process. Two types of aluminum alloy powders (Al-4.99Si-1.05Cu-0.47Mg and Al-7Mg) are employed for the 3D printing-based combined method. Nine types of Al-Si-Cu-Mg alloys are manufactured using the combined method, and the relationship between their microstructures and properties is examined.

The CoCrFeMnNi high-entropy alloy (HEA), which is the most widely known HEA with a single facecentered cubic structure, has attracted significant academic attention over the past decade owing to its outstanding multifunctional performance. Recent studies have suggested that CoCrFeMnNi-type HEAs exhibit excellent printability for selective laser melting (SLM) under a wide range of process conditions. Moreover, it has been suggested that SLM can not only provide great topological freedom of design but also exhibit excellent mechanical properties by overcoming the strength–ductility trade-off via producing a hierarchical heterogeneous microstructure. In this regard, the SLM-processed CoCrFeMnNi HEA has been extensively studied to comprehensively understand the mechanisms of microstructural evolution and resulting changes in mechanical properties. In this review, recent studies on CoCrFeMnNi-type HEAs produced using SLM are discussed with respect to process-induced microstructural evolution and the relationship between hierarchical heterogeneous microstructure and mechanical properties.

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• Investigation of effects of process parameters on microstructure and fracture toughness of SLM CoCrFeMnNi
  Joseph Agyapong, Diego Mateos, Aleksander Czekanski, Solomon Boakye-Yiadom
  Journal of Alloys and Compounds.2024; 987: 173998.     CrossRef
• Cryogenic Tensile Behavior of Ferrous Medium-entropy Alloy Additively Manufactured by Laser Powder Bed Fusion
  Seungyeon Lee, Kyung Tae Kim, Ji-Hun Yu, Hyoung Seop Kim, Jae Wung Bae, Jeong Min Park
  journal of Korean Powder Metallurgy Institute.2024; 31(1): 8.     CrossRef
• Data-driven Approach to Explore the Contribution of Process Parameters for Laser Powder Bed Fusion of a Ti-6Al-4V Alloy
  Jeong Min Park, Jaimyun Jung, Seungyeon Lee, Haeum Park, Yeon Woo Kim, Ji-Hun Yu
  journal of Korean Powder Metallurgy Institute.2024; 31(2): 137.     CrossRef
• Cryogenic tensile behavior of carbon-doped CoCrFeMnNi high-entropy alloys additively manufactured by laser powder bed fusion
  Haeum Park, Hyeonseok Kwon, Kyung Tae Kim, Ji-Hun Yu, Jungho Choe, Hyokyung Sung, Hyoung Seop Kim, Jung Gi Kim, Jeong Min Park
  Additive Manufacturing.2024; 86: 104223.     CrossRef
• High-speed manufacturing-driven strength-ductility improvement of H13 tool steel fabricated by selective laser melting
  Yeon Woo Kim, Haeum Park, Young Seong Eom, Dong Gill Ahn, Kyung Tae Kim, Ji-hun Yu, Yoon Suk Choi, Jeong Min Park
  Powder Metallurgy.2023; 66(5): 582.     CrossRef

SiAlON-based ceramics are a type of oxynitride ceramics, which can be used as cutting tools for heatresistant super alloys (HRSAs). These ceramics are derived from Si3N4 ceramics. SiAlON can be densified using gaspressure reactive sintering from mixtures of oxides and nitrides. In this study, we prepare an α-/β-SiAlON ceramic composite with a composition of Yb_0.03Y_0.10Si_10.6Al_1.4O1.0N_15.0. The structure and mechanical/thermal properties of the densified SiAlON specimen are characterized and compared with those of a commercial SiAlON cutting tool. By observing the crystallographic structures and microstructures, the constituent phases of each SiAlON ceramic, such as α- SiAlON, β-SiAlON, and intergranular phases, are identified. By evaluating the mechanical and thermal properties, the contribution of the constituent phases to these properties is discussed as well.

In this study, AlSi10Mg powders with average diameters of 44 μm are additively manufactured into bulk samples using a selective laser melting (SLM) process. Post-heat treatment to reduce residual stress in the as-synthesized sample is performed at different temperatures. From the results of a tensile test, as the heat-treatment temperature increases from 270 to 320°C, strength decreases while elongation significantly increases up to 13% at 320°C. The microstructures and tensile properties of the two heat-treated samples at 290 and 320°C, respectively, are characterized and compared to those of the as-synthesized samples. Interestingly, the Si-rich phases that network in the as-synthesized state are discontinuously separated, and the size of the particle-shaped Si phases becomes large and spherical as the heat-treatment temperature increases. Due to these morphological changes of Si-rich phases, the reduction in tensile strengths and increase in elongations, respectively, can be obtained by the post-heat treatment process. These results provide fundamental information for the practical applications of AlSi10Mg parts fabricated by SLM.

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• Wear behavior of aluminum-matrix particle (TiH2 and ZrH2)-reinforced composite foam additively manufactured using directed energy deposition
  Hwa-Jeong Kim, Gwang-Yong Shin, Ki-Yong Lee, Do-Sik Shim
  Journal of Materials Research and Technology.2023; 25: 222.     CrossRef
• Effect of Microstructural Evolution on Mechanical Properties and Fracture Modes of AlSi10Mg Blocks Fabricated by Selective Laser Melting after Stress Relief Annealing
  Jianzhu Li, Yujie Li, Zhe Wang, Changguang Li, Hai Yuan, Yun Hao
  Advanced Engineering Materials.2022;[Epub]     CrossRef

High-entropy alloys (HEAs) are generally defined as solid solutions containing at least 5 constituent elements with concentrations between 5 and 35 atomic percent without the formation of intermetallic compounds. Currently, HEAs receive great attention as promising candidate materials for extreme environments due to their potentially desirable properties that result from their unique structural properties. In this review paper, we aim to introduce HEAs and explain their properties and related research by classifying them into three main categories, namely, mechanical properties, thermal properties, and electrochemical properties. Due to the high demand for structural materials in extreme environments, the mechanical properties of HEAs including strength, hardness, ductility, fatigue, and wear resistance are mainly described. Thermal and electrochemical properties, essential for the application of these alloys as structural materials, are also described.

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• Composites of equiatomic Y, La, Ce, Nd, and Gd rare earth oxides: Chemical-shift effects and valence spectra
  Jungsu Bin, Hyunbae Gee, Taesung Park, UiJun Go, Jeoung Han Kim, Youn-Seoung Lee
  Current Applied Physics.2024; 59: 85.     CrossRef
• Sintering Behavior and Mechanical Property of Transition Metal Carbide-Based Cermets by Spark Plasma Sintering
  Jeong-Han Lee, Hyun-Kuk Park, Sung-Kil Hong
  Korean Journal of Materials Research.2022; 32(1): 44.     CrossRef

The objective of this study is to investigate the influence of powder shape and densification mechanism on the microstructure and mechanical properties of Ti-6Al-4V components. BE powders are uniaxially and isostatically pressed, and PA ones are injection molded because of their high strengths. The isostatically compacted samples exhibit a density of 80%, which is higher than those of other samples, because hydrostatic compression can lead to higher strain hardening. Owing to the higher green density, the density of BE-CS (97%) is found to be as high as that of other samples (BE-DS (95%) and P-S (94%)). Furthermore, we have found that BE powders can be consolidated by sintering densification and chemical homogenization, whereas PA ones can be consolidated only by simple densification. After sintering, BE-CS and P-S are hot isostatically pressed and BE-DS is hot forged to remove residual pores in the sintered samples. Apparent microstructural evolution is not observed in BE-CSH and P-SH. Moreover, BE-DSF exhibits significantly fine grains and high density of low-angle grain boundaries. Thus, these microstructures provide Ti-6Al-4V components with enhanced mechanical properties (tensile strength of 1179 MPa).

Over the last decade, the next generation’s ultra-high-temperature materials as an alternative to Nickel-based superalloys have been highlighted. Ultra-high-temperature materials based on refractory metals are one of several potential candidates. In particular, molybdenum alloys with small amounts of silicon and boron (Mo-Si-B alloys) have superior properties at high temperature. However, research related to Mo-Si-B alloys were mainly conducted by several developed countries but garnered little interest in Korea. Therefore, in this review paper, we introduce the development history of Mo-Si-B alloys briefly and discuss the properties, particularly the mechanical and oxidation properties of Mo-Si-B alloys. We also introduce the latest research trends of Mo-Si-B alloys based on the research paper. Finally, for domestic research related to this field, we explain why Mo-Si-B alloys should be developed and suggest the potential directions for Mo-Si-B alloys research.

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• Thermal Stability and Weight Reduction of Al0.75V2.82CrZr Refractory High Entropy Alloy Prepared Via Mechanical Alloying
  Minsu Kim, Hansung Lee, Byungmin Ahn
  journal of Korean Powder Metallurgy Institute.2023; 30(6): 478.     CrossRef
• Preparation and Structure of Chromium Coatings Doped with Diamond Nanoparticles Deposited Directly on a Monolithic Composite of Molybdenum and Aluminum
  V. P. Petkov, M. K. Aleksandrova, R. V. Valov, V. P. Korzhov, V. M. Kiiko, I. S. Zheltyakova
  Protection of Metals and Physical Chemistry of Surfaces.2023; 59(3): 396.     CrossRef
• A Review of Mo-Si Intermetallic Compounds as Ultrahigh-Temperature Materials
  Liang Jiang, Bin Zheng, Changsong Wu, Pengxiang Li, Tong Xue, Jiandong Wu, Fenglan Han, Yuhong Chen
  Processes.2022; 10(9): 1772.     CrossRef
• Heat-Resistant Molybdenum Borosilicate Alloys Hardened with Titanium Carbides: Mo–Si–B–TiC (Survey)
  I. L. Svetlov, O. G. Ospennikova, M. I. Karpov, Yu. V. Artemenko
  Inorganic Materials: Applied Research.2021; 12(4): 866.     CrossRef

In this study, two types of SKD61 tool-steel samples are built by a selective laser melting (SLM) process using the different laser scan speeds. The characteristics of two kinds of SKD61 tool-steel powders used in the SLM process are evaluated. Commercial SKD61 tool-steel power has a flowability of 16.68 sec/50 g and its Hausner ratio is calculated to be 1.25 by apparent and tapped density. Also, the fabricated SKD61 tool steel powder fabricated by a gas atomization process has a flowability of 21.3 sec/50 g and its Hausner ratio is calculated to be 1.18. Therefore, we confirmed that the two powders used in this study have excellent flowability. Samples are fabricated to measure mechanical properties. The highest densities of the SKD61 tool-steel samples, fabricated under the same conditions, are 7.734 g/cm³ (using commercial SKD61 powder) and 7.652 g/cm³ (using fabricated SKD61 powder), measured with Archimedes method. Hardness is measured by Rockwell hardness testing equipment 5 times and the highest hardnesses of the samples are 54.56 HRC (commercial powder) and 52.62 HRC (fabricated powder). Also, the measured tensile strengths are approximately 1,721 MPa (commercial SKD61 powder) and 1,552 MPa (fabricated SKD61 powder), respectively.

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• Microstructural effects on the tensile and fracture behavior of selective laser melted H13 tool steel under varying conditions
  Jungsub Lee, Jungho Choe, Junhyeok Park, Ji-Hun Yu, Sangshik Kim, Im Doo Jung, Hyokyung Sung
  Materials Characterization.2019; 155: 109817.     CrossRef

In this study, H13 tool steel sculptures are built by a metal 3D printing process at various laser scan speeds. The properties of commercial H13 tool steel powders are confirmed for the metal 3D printing process used: powder bed fusion (PBF), which is a selective laser melting (SLM) process. Commercial H13 powder has an excellent flowability of 16.68 s/50 g with a Hausner ratio of 1.25 and a density of 7.68 g/cm³. The sculptures are built with dimensions of 10 × 10 × 10 mm3 in size using commercial H13 tool steel powder. The density measured by the Archimedes method is 7.64 g/cm³, similar to the powder density of 7.68 g/cm³. The hardness is measured by Rockwell hardness equipment 5 times to obtain a mean value of 54.28 HRC. The optimum process conditions in order to build the sculptures are a laser power of 90 W, a layer thickness of 25 μm, an overlap of 30%, and a laser scan speed of 200 mm/s.

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• Spheroidization of Enamel Powders by Radio Frequency Plasma Treatment and Application to Additive Manufacturing
  Ki-Bong Kim, Dong-Yeol Yang, Yong-Jin Kim, Jungho Choe, Ji-Na Kwak, Woo-Hyung Jung
  Journal of Korean Powder Metallurgy Institute.2020; 27(5): 388.     CrossRef
• Microstructural effects on the tensile and fracture behavior of selective laser melted H13 tool steel under varying conditions
  Jungsub Lee, Jungho Choe, Junhyeok Park, Ji-Hun Yu, Sangshik Kim, Im Doo Jung, Hyokyung Sung
  Materials Characterization.2019; 155: 109817.     CrossRef
• Nano-mechanical Behavior of H13 Tool Steel Fabricated by a Selective Laser Melting Method
  Van Luong Nguyen, Eun-ah Kim, Jaecheol Yun, Jungho Choe, Dong-yeol Yang, Hak-sung Lee, Chang-woo Lee, Ji-Hun Yu
  Metallurgical and Materials Transactions A.2019; 50(2): 523.     CrossRef
• Correlation between Microstructure and Mechanical Properties of the Additive Manufactured H13 Tool Steel
  Woojin An, Junhyeok Park, Jungsub Lee, Jungho Choe, Im Doo Jung, Ji-Hun Yu, Sangshik Kim, Hyokyung Sung
  Korean Journal of Materials Research.2018; 28(11): 663.     CrossRef
• Evaluation of Strain-Rate Sensitivity of Selective Laser Melted H13 Tool Steel Using Nanoindentation Tests
  Van Nguyen, Eun-ah Kim, Seok-Rok Lee, Jaecheol Yun, Jungho Choe, Dong-yeol Yang, Hak-sung Lee, Chang-woo Lee, Ji-Hun Yu
  Metals.2018; 8(8): 589.     CrossRef
• Comparison of Nano-Mechanical Behavior between Selective Laser Melted SKD61 and H13 Tool Steels
  Jaecheol Yun, Van Nguyen, Jungho Choe, Dong-Yeol Yang, Hak-Sung Lee, Sangsun Yang, Ji-Hun Yu
  Metals.2018; 8(12): 1032.     CrossRef
• A study about sculpture characteristic of SKD61 tool steel fabricated by selective laser melting(SLM) process
  Jaecheol Yun, Jungho Choe, Ki-Bong Kim, Sangsun Yang, Dong-Yeol Yang, Yong-Jin Kim, Chang-Woo Lee, Chang-Woo Lee
  Journal of Korean Powder Metallurgy Institute.2018; 25(2): 137.     CrossRef

A powder-in-sheath rolling (PSR) process utilizing a copper alloy tube was applied to a fabrication of a multi-walled carbon nanotube (CNT) reinforced aluminum matrix composite. A copper tube with an outer diameter of 30 mm and a wall thickness of 2 mm was used as a sheath material. A mixture of pure aluminum powders and CNTs with the volume contents of 1, 3, 5 vol% was filled in the tube by tap filling and then processed to 93.3% height reduction by a rolling mill. The relative density of the CNT/Al composite fabricated by the PSR decreased slightly with increasing of CNTs content, but showed high value more than 98%. The average hardness of the 5%CNT/Al composite increased more than 3 times, compared to that of unreinforced pure Al powder compaction. The hardness of the CNT/Al composites was some higher than that of the composites fabricated by PSR using SUS304 tube. Therefore, it is concluded that the type of tube affects largely on the mechanical properties of the CNT/Al composites in the PSR process.

A powder-in-sheath rolling method was applied to a fabrication of a carbon nano tube (CNT) reinforced aluminum composite. A STS304 tube with an outer diameter of 34 mm and a wall thickness of 2 mm was used as a sheath material. A mixture of pure aluminum powders and CNTs with the volume contents of 1, 3, 5 vol was filled in the tube by tap filling and then processed to 73.5% height reduction by a rolling mill. The relative density of the CNT/ Al composite fabricated by the powder-in-sheath rolling decreased slightly with increasing of CNTs content, but exhibited high value more than 98. The grain size of the aluminum matrix was largely decreased with addition of CNTs; it decreased from 24 μm to 0.9 μm by the addition of only 1 volCNT. The average hardness of the composites increased by approximately 3 times with the addition of CNTs, comparing to that of unreinforced pure aluminum. It is concluded that the powder-in-sheath rolling method is an effective process for fabrication of CNT reinforced Al matrix composites.

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• Microstructure and Mechanical Properties of CNT/Al Composite Fabricated by a Powder-in-Sheath Rolling Method utilizing Copper Tube as a Sheath
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