Kim, Woo Hyeok, Hajra, Raj Narayan, Park, Hyung-Ki, Yun, Jung-Yeul, Kim, Jeoung Han.

This paper reports a novel and scalable approach for fabricating oxide dispersion-strengthened (ODS) Ti-6Al-4V (Ti64) alloys using bound metal deposition (BMD). Traditionally, ODS alloys are produced through mechanical alloying, which is time-intensive, contamination-prone, and difficult to scale. This study describes an alternative route in which Y₂O₃ nanoparticles are precipitated directly within spherical Ti64 powders during electrode induction gas atomization. Here, these powders (reinforced in situ) were blended with a dual-binder system, pelletized, and used as feedstock for extrusion-based BMD additive manufacturing (AM). Post-processing involved solvent and thermal de-binding followed by vacuum sintering at different temperatures. Microstructural analysis confirmed the spherical morphology of the powders and uniform dispersion of nano-sized Y₂O₃ particles. The sintered parts retained their shape fidelity, and the microstructure transitioned from acicular α′-martensite at 950 ◦C to equiaxed α+ β phases at higher temperatures. High-resolution transmission electron microscopy indicated the following crystallographic orientation relationship in the tested system: (1100)Ti // (400)Y₂O₃ and [1120]Ti // [011]Y₂O₃. The finest oxide particles (20–80 nm) and highest hardness (~391 HV) were observed for the system sintered at 950 ℃. The proposed process eliminates the need for mechanical alloying and yields highly flowable and uniform ODS powders ideal for AM. The integration of gas atomization and BMD results in a new, clean, and efficient pathway for producing high-performance Ti-based ODS components with potential application in aerospace, biomedical, and energy systems.

Journal of alloys and compounds, v.1050, 2026년, pp.185574 -   

Taehyeob Im1 · Minjong Kim1 · Jonghyeok Ahn1 · Suyeon Kim2 · Hansol Lee1 · Kwiyoung Lee1 · Dongju Lee2 ·Jai-Sung Lee1 · Jongryoul Kim1 · Caroline Sunyong Lee1

1 Department of Materials and Chemical Engineering, Hanyang University ERICA, Ansan, Republic of Korea

2 Department of Advanced Materials Engineering, Chungbuk National University, Cheongju, Republic of Korea

A novel hybrid manufacturing approach combining dual-nozzle material extrusion and spark plasma sintering to fabricate metal–insulator–metal (MIM)-structured Fe-6.5 wt% Si (Fe-6.5Si) magnetic cores. Unlike conventional stamping processes, which involve rolling, insulating, punching, and stacking thin Fe-6.5Si sheets, the proposed method simplifies fabrication into fewer steps, eliminates material waste from scrap, and supports a more sustainable manufacturing route. This process integrates MgO-B2O3-SiO2 (MBS) insulation layers to achieve enhanced bonding between the layers. The manufacturing process involved integrating MBS insulation for structural integrity, reducing the Fe-6.5Si layer thickness for frequency stability, and applying a post-heat treatment to improve magnetic performance. The MBS insulation system demonstrated sinterability, forming stable interfaces with the Fe-6.5Si layers. Through experimental investigation, it was found that a Fe-6.5Si layer thickness of 0.6 mm combined with 0.2 mm MBS insulation layers exhibited promising frequency stability up to 1 kHz. Additionally, post-heat treatment at 1200 °C enhances the magnetic properties by increasing the permeability and reducing hysteresis loss through grain growth and interface modification. This hybrid manufacturing approach has the potential to produce high-performance magnetic cores while offering design possibilities for electromagnetic components.

November 2025International Journal of Precision Engineering and Manufacturing-Green Technology

Do Won Lee a , Jeong Ah Lee a , Hyojin Park a, Rae Eon Kim b, Jungho Choe c, Sun Ig Hong d ,Hyoung Seop Kim a,b,e,f,*

a Department of Materials Science and Engineering, Pohang University of Science and Technology (POSTECH), Pohang, 37673, Republic of Korea

b Graduate Institute of Ferrous Technology, Pohang University of Science and Technology (POSTECH), Pohang, 37673, Republic of Korea

c Department of 3D Printing Materials, Korea Institute of Materials Science (KIMS), Changwon, 51508, Republic of Korea

d Department of Materials Science and Engineering, Chungnam National University, Daejeon, 34134, Republic of Korea

e Center for Heterogenic Metal Additive Manufacturing, Pohang University of Science and Technology (POSTECH), Pohang 37673, Republic of Korea

f Advanced Institute for Materials Research (WPI-AIMR), Tohoku University, Sendai, 980-8577, Japan

High-entropy alloys (HEAs), known for their superior mechanical properties and compositional flexibility, are increasingly being explored for sintering-based additive manufacturing processes, such as material extrusion (MEX), which offers cost-effective production of complex geometries. However, the mechanical performance of MEX-fabricated HEAs has been limited by residual porosity and oxide layers, which are typically seen as detrimental. In this study, we present a novel perspective on these features, demonstrating how pores and thin oxide layers act as barriers to dislocation motion, enhancing strain hardening through hetero-deformation induced (HDI) strengthening. Finite element method analyses reveal that pores act as stress concentrators, leading to localized dislocation accumulation and strain hardening, while experimental results highlight the activation of twinning mechanisms that further boost mechanical performance. As a result, the MEX-fabricated CoCrFeMnNi HEA exhibits a yield strength of 245 MPa, an ultimate tensile strength of 538 MPa, and a fracture elongation of 30.3%, comparable to or exceeding those of conventionally processed HEAs. HDI strengthening contributes approximately 55%, confirming its significant role in enhancing mechanical performance despite the presence of porosity. These findings challenge the conventional notion that porosity and oxide layers degrade mechanical properties, instead demonstrating their potential as effective strengthening mechanisms. This study provides critical insights into the process-structure-property relationships in MEX-fabricated HEAs, offering a new pathway to optimizing mechanical performance without additional densification processes.

Materials Science & Engineering A 940 (2025) 148579

Jinhee Bae, Seungki Jo, Soo-ho Jung, Jong Min Park, Cheol Min Kim, Kwi-Il Park, and Kyung Tae Kim* (KIMS)

Using three-dimensional (3D) printing technology to fabricate Bi2Te3-based thermoelectric (TE) generators opens a potential way to create shape-conformable devices capable of recovering waste heat from thermal energy sources with diverse surface morphologies. However, pores formed in 3D-printed Bi2Te3-based materials by the removal of the organic ink binder result in unsatisfactory performance compared to the bulk materials, which has limited the widespread application of the ink-based 3D printing process. Furthermore, managing the volatile Se element in the n-type materials poses significant technological challenges compared to the p-type counterparts, resulting in a scarcity of research on 3D printing of n-type Bi2Te3. Here, we synthesized edge-oxidized graphene (EOG)-incorporated Se-free n-type Bi1.7Sb0.3Te3 (BST) using a direct ink writing (DIW) process with a binder-free novel ink. The incorporated EOG provides connectivity between small BST grains separated by pores and induces a bimodal-like grain structure during the DIW and sintering process. The optimal EOG content of 0.1 wt % in 3D-printed n-type BST simultaneously achieved both carrier transport control and active phonon scattering, due to its unique microstructure. A maximum ZT of 0.71 was obtained in the 0.1 wt % EOG/BST materials at 448 K, comparable to commercial bulk n-type Bi2Te3-based materials. Further, a single-element device composed of the EOG-BST material exhibited a 2-fold improvement in performance compared to pure-BST. These results open a technological route for the application of 3D printing technology for ink-based TE materials.

ACS applied materials & interfaces, v.16 no.36, 2024년, pp.47844 - 47853

2026년 04월 01 ~ 03일

이번에 학회에서는 아래와 같이 3가지 내용에 대해서 발표하였습니다.

1. MEX 공법을 이용한 순수 구리 기반 콜드 플레이트 개발, 김주용, 임태협, 이선영, 리프로텍, Hanyang University ERICA (첨부파일)

2. 재료 압출 적층제조 공정을 적용한 Hastelloy C22 다공체의 소결 온도 변화를 통한 기공 제어와 그 가스 투과 특성 및 기계적 거동, 오주환, 박소연, 윤중열, 김주용, 이기안, 인하대학교, 한국재료연구원, 리프로텍

3. 재료 압출 적층 제조(MEX) 공정과 급속 냉각 열간 정수압 가압 열처리(URQ-HIP) 공정을 활용한 석출경화형 스테인리스강(17-4PH)의 물성 향상 연구, 조용훈, 전주현, 김주용, 이기안, 인하대학교, Quintus Technologies Korea, 리프로텍

앞으로도 꾸준히 연구성과를 공유하도록 하겠습니다. 

Fabrication of the CM247LC Ni-based superalloy using metal-material extrusion additive manufacturing and its microstructure and mechanical properties

Kyung-Un Won, Ju-Yong Kim, Jung-Yeul Yun, Seong-Moon Seo, Suk-Hwan Kwon, and Kee-Ahn Lee

Abstract

CM247LC has been widely recognised as a difficult-to-process material for laser-based additive manufacturing processes such as laser powder bed fusion and direct energy deposition. The material extrusion additive manufacturing (MEAM) process involves the melting and extrusion of a feedstock composed of a polymer binder and metal powder to fabricate a green body, followed by debinding and sintering to achieve the final component with the desired geometry. In this study, CM247LC alloy was fabricated using a MEAM process, and its microstructural characteristics and mechanical properties were investigated. The sintered specimens exhibited a relative density exceeding 90%, with inter-layer defects and closed pores observed in the microstructure. Post-sintering analysis confirmed the formation of γ’ precipitates and MC carbides within the matrix, with MC carbides predominantly distributed along grain boundaries and concentrated on the surfaces of closed pores. The fabricated specimens exhibited an increased carbon content compared to the initial powder, attributed to excessive MC carbide formation during sintering. This was caused by the reaction between carbon from the binder and carbide-forming elements in the metal powder. Room temperature tensile tests on defect-free specimens yielded a yield strength of 660.4 MPa, an ultimate tensile strength of 891 MPa, and an elongation of 7.56%, with mechanical properties exhibiting significant variation depending on specimen conditions. This variability was mainly attributed to the susceptibility of inter-layer crack initiation under applied stress. Furthermore, this study discussed the deformation and fracture mechanisms of MEAM-processed CM247LC alloy and assessed the feasibility of fabricating difficult-to-form Ni-based superalloys via the non-fusion MEAM process.

Powder Metallurgy, 

Min-Ji Kim 1,2, Min-Jeong Lee 1,2, Hyun-Ju Kim 1, Ju-Yong Kim 3,

Jung-Woo Lee 2*, Jung-Yeul Yun 1*

Metal powder filters are key components in semiconductor manufacturing equipment that play a critical role in preventing

the ingress of impurities and fine particles that may be contained in process gases. With the increasingly advanced development

of the semiconductor industry, metal powder filters also require more precise and advanced performance. Therefore, in this study,

a filter with a honeycomb structure morphology with crossed top and bottom was fabricated by a material extrusion additive

manufacturing (MEAM) process. To achieve this, the prepared pellets were subjected to the MEAM, allowing the creation of filters

with complex shapes featuring crossed top and bottom structures. After polishing the surface of the specimen, solvent debinding

and thermal debinding were performed to remove the binder. Solvent debinding was performed in n-Heptane for 24 hours, while

thermal debinding was performed in an Ar atmosphere at a maximum temperature of 800°C. The debinded specimens were sintered

under a high vacuum atmosphere at temperatures of 850°C, 950°C, and 1050°C, respectively. The prepared metal powder filters

were examined for filter morphology and microstructure using optical microscopy, and pore properties such as porosity and air

permeability were evaluated.

Keywords: Metal Powder Filters; Sintering; Porosity; Air Permeability; Material Extrusion Additive Manufacturing (MEAM)

https://imim.pl/files/archiwum/Vol3_2025/16.pdf

Minji Kim1,2, Min-Jeong Lee1,2, Su-Jin Yun1, Poong-Yeon Kim1, Hyeon Ju Kim1, Juyong Kim3, Jung Woo Lee2,*, Jung-Yeul Yun1,*

Abstract

• The development of high-performance metal filters is essential for maintaining ultra-clean environments in semiconductor manufacturing. In this study, cross-sealed honeycomb filters were fabricated using STS316L powder via material extrusion additive manufacturing (MEAM) for semiconductor gas filtration. The effects of filter geometry (4 or 9 channels) and sintering temperature (850°C, 950°C, or 1,050°C) on performance were examined. First, 4-channel and 9-channel filters sintered at the same temperature (950°C) exhibited similar porosities of 50.08% and 50.57%, but the 9-channel filter showed a higher pressure-drop (0.26 bar) and better filtration-efficiency (3.55 LRV) than the 4-channel filter (0.19 bar and 3.25 LRV, respectively). Second, for filters with the same geometry (4-channel) increasing the sintering temperature reduced porosity from 64.52% to 40.33%, while the pressure-drop increased from 0.13 bar to 0.22 bar and filtration-efficiency improved from 2.53 LRV to 3.51 LRV. These findings demonstrate that filter geometry and sintering temperature are key factors governing the trade-off between air permeability, pressure-drop, and filtration efficiency. This work provides insights and data for optimizing MEAM-based high-performance metal powder filter design.
• Keywords: Material Extrusion Additive Manufacturing (MEAM); Metal Filter; STS316L; Porosity; Sintering
• 

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Yong-Hoon Cho a, So-Yeon Park a, Ju-Yong Kim b, Jung-Yeul Yun c, Kee-Ahn Lee a

Abstract

This study investigates the effect of H900 heat treatment on the microstructure and corrosion behavior of 17-4 PH stainless steel fabricated via metal material extrusion (MEX) additive manufacturing. Samples were produced through the MEX process, and the as-sintered condition was compared against specimens subjected to a standard H900 heat treatment. Corrosion properties were systematically evaluated using cyclic potentiodynamic polarization and electrochemical impedance spectroscopy in a 3.5 wt% NaCl solution, coupled with multi-scale microstructural characterization. The as-sintered samples exhibited approximately 2.6 % porosity and oxide inclusions, along with Cu segregation at δ-Fe/martensite phase boundary, and 10–20 nm Cu-rich precipitates (CRPs). While heat treatment did not significantly alter the defect fraction, it refined the martensitic grain structure, eliminated Cu segregation, promoted additional NbC precipitation, and modified the CRPs into finer, coherent particles. Consequently, the H900 specimen demonstrated superior corrosion resistance, evidenced by an increase in the corrosion potential by approximately +0.04 V and the breakdown potential by approximately +0.13 V. Post-corrosion analysis revealed that pores and oxide inclusions acted as primary sites for pitting corrosion. The enhanced corrosion resistance of the H900 specimen is attributed to the formation of a denser, more stable passive film, resulting from microstructural homogenization, grain refinement, and the elimination of a Cr-depleted zone beneath the film. These findings confirm that heat treatment is critical for optimizing the performance of MEX-fabricated 17-4 PH steel.

Keywords: 

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Do Won Lee^a, Jeong Ah Lee^a, Hyojin Park^a, Rae Eon Kim^b, Jungho Choe^c, Sun Ig Hong^d, Hyoung Seop Kim^a,b,e,f,*

ABSTRACT

High-entropy alloys (HEAs), known for their superior mechanical properties and compositional flexibility, are increasingly being explored for sintering-based additive manufacturing processes, such as material extrusion (MEX), which offers cost-effective production of complex geometries. However, the mechanical performance of MEX-fabricated HEAs has been limited by residual porosity and oxide layers, which are typically seen as detrimental. In this study, we present a novel perspective on these features, demonstrating how pores and thin oxide layers act as barriers to dislocation motion, enhancing strain hardening through hetero-deformation induced (HDI) strengthening. Finite element method analyses reveal that pores act as stress concentrators, leading to localized dislocation accumulation and strain hardening, while experimental results highlight the activation of twinning mechanisms that further boost mechanical performance. As a result, the MEX-fabricated CoCrFeMnNi HEA exhibits a yield strength of 245 MPa, an ultimate tensile strength of 538 MPa, and a fracture elongation of 30.3%, comparable to or exceeding those of conventionally processed HEAs. HDI strengthening contributes approximately 55%, confirming its significant role in enhancing mechanical performance despite the presence of porosity. These findings challenge the conventional notion that porosity and oxide layers degrade mechanical properties, instead demonstrating their potential as effective strengthening mechanisms. This study provides critical insights into the process-structure-property relationships in MEX-fabricated HEAs, offering a new pathway to optimizing mechanical performance without additional densification processe

Keywords: High-entropy alloy, Material extrusion, Additive manufacturing, Tensile deformation, Strain hardening

링크보기

Noh-Geon Song, So-Yeon Park, Jung-Yeul Yun, Ju-Yong Kim, Kee-Ahn Lee

Abstract

This study introduces a novel method for manufacturing porous SUS316L using the metal material extrusion (MEX) process and examines the effects of the powder particle size on the pore structure, gas flowability, and mechanical properties. SUS316L foams were fabricated using powders with average sizes of 50 μm and 8 μm. Open pore diameters were approximately 10 μm for the 50 μm foam and 2 μm for the 8 μm foam. Gas flowability measurements revealed that the 50 μm foam exhibited slope values suitable for filtration applications, whereas the 8 μm foam showed lower flowability due to a reduced pore fraction and size. Compressive testing indicated yield strengths of 82.57 MPa and 141.33 MPa for the 50 μm and 8 μm foams, respectively, demonstrating superior strength-to-weight ratios compared to SUS316L foams fabricated by conventional methods and surpassing the mechanical performance of commercial 316L filters manufactured by powder metallurgy process. These findings highlight the capability of MEX in producing porous SUS316L structures with tunable pores and mechanical properties for various applications.

Keywords

Material extrusion additive manufacturing, 316L Stainless steel, Foam, Compressive property,Gas flowability.

링크보기

Yong-Hoon Cho a, So-Yeon Park a, Ju-Yong Kim b, Kee-Ahn Lee a,*

A b s t r a c t

The current study intended to manufacture 17-4PH stainless steel using material extrusion additive manufacturing (MEAM) process and to control the microstructure and mechanical properties of the steel through heat treatment. The as sintered MEAM 17-4PH steel was densely manufactured with a 97% or more sintered density and few inter-layer defects. Microstructure images of the prepared specimen showed an isotropic microstructure, and the matrix was mainly composed of lath martensite. After heat treatment (a standard H900 condition), no phase change was observed in the matrix of the specimen, and the dislocation density slightly increased. In the case of nano-sized particles, 16.38 nm 3R structure Cu-rich precipitates (CRP) and some NbC were present in the as sintered steel. A high fraction of BCC structure CRP of size 3.51 nm and NbC of size about 88 nm precipitated in the post-heat-treated specimen. Tensile test of the specimen before the heat treatment (as sintered) showed the best mechanical properties among the MEAM 17-4PH steels reported so far. After the heat treatment, tensile strength, yield strength, and elongation even increased to 1.35 GPa, 1.11 GPa, and 7.8%, respectively. This study also aimed to suggest a method for controlling the properties of the MEAM-built 17-4PH stainless steel to improve its mechanical properties based on its microstructures change and the difference in strengthening mechanisms.

© 2023 The Authors. Published by Elsevier B.V. This is an open access article under the CC

BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/).

Keywords: Material extrusion additive, manufacturing, 17-4PH stainless steel, Post heat-treatment, Microstructure, Tensile property, Strengthening mechanism

링크보기

Yu-Jeong Yi 1,2, Min-Jeong Lee 1,2, Su-Jin Yun 1, Manho Park 3,Ju-Yong Kim 4, Jungwoo Lee 2*, Jung-Yeul Yun 1*

Recently, 3D printing processes have been used to manufacture metal powder filters with manufacturing complex-shape. In

this study, metal powder filters of various shapes were manufactured using the metal extrusion additive manufacturing (MEAM)

process, which is used to manufacture three-dimensional structures by extruding a filament consisting of a metal powder and

a binder. Firstly, filaments were prepared by appropriately mixing SUS316 powder with sizes ranging from 7.5 μm to 50 μm

and a binder. These filaments were extruded at temperatures of 100℃ to 160℃ depending on the type of filament being manufactured,

to form three types of cylindrical filter. Specimens were sintered in a high vacuum atmosphere furnace at 850℃ to 1050℃

for 1 hour after debinding. The specimens were analyzed for permeability using a capillary flow porometer, porosity was determined

by applying Archimedes’ law and microstructure was observed using SEM.

Keywords: Gas Filter; Additive manufacturing; Stainless steel; Porosity; Powder size

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Taehyeob Im, Suyeon Kim, Juyong Kim, Minjong Kim, Jonghyeok Ahn, Kwiyoung Lee, Dongju Lee, Jai-Sung Lee, Jongryoul Kim & Caroline Sunyong Lee 

ABSTRACT 

This study proposes a novel approach for fabricating Fe-6.5 wt. %Si (Fe-6.5Si) soft magnetic cores using a dual-nozzle material extrusion (MEX) three-dimensional (3D) printing technology followed by a spark plasma sintering (SPS) process. A SiO2 insulator was printed between the Fe-6.5Si layers to fabricate metal–insulator-metal (MIM)-structured cores. Densified Fe-6.5Si soft magnetic cores (over 99%) were obtained owing to the resolution of the sintering problem with Fe-6.5Si because of its brittle nature using SPS. The magnetic core with a 0.2 mm-printed insulator (MC0.2) achieved a uniform insulator thickness of approximately 85 μm. Despite MC0.2 being approximately three times thicker than the single Fe-6.5Si layer (magnetic core single layer, MCS), a SiO2 insulator used in the cores of MC0.2 and MCS, resulted in comparable eddy current losses at 1 kHz. This highlighted the effectiveness of the MIM structure in suppressing the eddy currents. Thus, the proposed approach offers a promising solution for overcoming the geometric limitations of traditional stamping processes and paves the way for advanced magnetic core applications in additive manufacturing. 

KEYWORDS 

Fe-6.5Si soft magnetic cores; dual-nozzle MEX 3D printing; spark plasma sintering; metal-insulator-metal structure; core loss 

링크보기

 Taehyeob Im a, Heungseok Oh a, Byeonghwa Goh b,c, Juyong Kim d, Jai-Sung Lee a, Joonmyung Choi b,c,**, Caroline Sunyong Lee a,* 

A B S T R A C T

This study introduces a post-treatment process, the subpressure-driven soft deformation method, to reduce inherent voids in Material Extrusion (MEX) components. By subjecting printed green components to heat treatment under subpressure, the process enhances viscosity, effectively filling voids formed between deposited tracks. The average porosities of the samples sintered from the green components without and with soft deformation are calculated to be 3.55% and 2.36%, respectively. A comparison of the tensile strengths and fracture surfaces of the sintered samples with and without soft deformation treatment indicated that the sintered samples with soft deformation treatment exhibited narrower standard deviation for the various mechanical properties. Capillary rheometer calculations indicate feedstock viscosity to be between 450.34 and 1018.31 Pa s under subpressure, diminishing inter-track voids without sizeable dimensional changes. Molecular dynamics simulation demonstrates a 3.7-fold increase in bond strength, indicating intertrack voids effectively eliminated. Reduced inter-particle distances facilitate necking, grain growth, and improved sintered density. 

 Keywords: Material extrusion (MEX) Inherent voids Subpressure-driven soft deformation All-atom molecular dynamics simulations 

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