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Application of direct laser metal tooling for AISI H13 tool stee

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中国有色金属学会会刊：英文版 2009年第B09期19卷 284-287页

作者： Jae-Ho LEE Jeong-Hwan JANG byeong-don joo Hong-Sup YIM Young-Hoon MOON School of Mechanical Engineering Pusan National University

In the die industry, it is commonly agreed that residual tool life can be successfully extended by timely repair of damaged surfaces. Traditionally, the main repair process is tungsten inert gas (TIG) welding, but a new process called direct laser metal tooling (DLMT) emerges. DLMT is a manual process, of which results depend on the materials of the powders and tools, the laser process and parameters. This technology is a direct-metal freeform fabrication technique in which a 200 W fiber laser is used. AISI H13 tool steel is a suitable material for die casting tools because of the high resistance to thermal fatigue and dimensional stability. In this research, AISI H13 tool steel was melted with metal powder by fiber laser. Before melting AISI H13, the powders were analyzed with XRF equipment. Then, hardness distribution of laser melted zone was investigated. The microstructure in laser melted zone was discussed. In order to identify the effect of particle size of powder on the melted zone, two types of particle sizes of powders were used. Experimental results show that the mold repair process using DLMT can be applied in the mold repair industry.

关键词：金属模具应用激光工具钢 H13 社会光纤激光器粉末材料修复过程

Laser surface hardening of AISI H13 tool steel

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中国有色金属学会会刊：英文版 2009年第4期19卷 917-920页

作者： Jae-Ho LEE Jeong-Hwan JANG byeong-don joo Young-Myung SON Young-Hoon MOON School of Mechanical Engineering Pusan National University

An attempt was made to improve the surface hardness and wear properties of AISI H13 tool steel through solid solution hardening and refinement of microstructures using a 200 W fiber laser as a heat generating *** hardness of laser melted zone was *** order to identify the effect of heat input on the laser melting zone,scanning conditions were *** results show that,the hardness of as-received AISI H13 tool steel is approximately Hv 240,and the hardness after laser surface heat treatment is around Hv *** hardening depth and width are increased with the increase in the heat input *** of experimental results will be considered in tooling industry.

关键词：激光表面硬化工具钢 H13 激光表面热处理表面硬度信息社会光纤激光器固溶强化

Selective laser melting of Fe-Ni-Cr layer on AISI H13 tool steel

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中国有色金属学会会刊：英文版 2009年第4期19卷 921-924页

作者： byeong-don joo Jeong-Hwan JANG Jae-Ho LEE Young-Myung SON Young-Hoon MOON School of Mechanical Engineering Pusan National University

An attempt to fabricate Fe-Ni-Cr coating on AISI H13 tool steel was performed with selective laser ***-Ni-Cr coating was produced by experimental facilities consisting of a 200 W fiber laser which can be focused to 80 μm and atmospheric chamber which can control atmospheric pressure with N2 or *** layer was fabricated with various process parameters such as laser power,scan rate and fill *** quality and coating thickness were measured and *** different surface patterns,such as typeⅠ,typeⅡand type Ⅲ,are shown with various test conditions and smooth regular pattern is obtained under the conditions as 10 μm of fill spacing,50-350 mm/s of scan rate and 40 μm of fill spacing,10-150 mm/s of scan *** maximum coating thickness is increased with power elevation or scan rate drop,and average thickness of 10 μm fill spacing is lower than that of 40 μm fill spacing.

关键词：镍铬涂层工具钢激光熔融社会扫描速度铁涂层厚度光纤激光器

Modified embedded-atom method interatomic potentials for Mg-Al-Ca and Mg-Al-Zn ternary systems

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Journal of Magnesium and Alloys 2021年第1期9卷 317-335页

作者： Hyo-Sun Jang donghyuk Seol byeong-joo Lee Department of Materials Science and Engineering Pohang University of Science and Technology(POSTECH)Pohang 37673Republic of Korea

Al,Ca,and Zn are representative commercial alloying elements for Mg *** investigate the effects of these elements on the deformation and recrystallization behaviors of Mg alloys,we develop interatomic potentials for the Al-Ca,Al-Zn,Mg-Al-Ca and Mg-Al-Zn systems based on the second nearest-neighbor modified embedded-atom method *** developed potentials describe structural,elastic,and thermodynamic properties of compounds and solutions of associated alloy systems in reasonable agreement with experimental data and higher-level *** applicability of these potentials to the present investigation is confirmed by calculating the generalized stacking fault energy for various slip systems and the segregation energy on twin boundaries of the Mg-Al-Ca and Mg-Al-Zn alloys,accompanied with the thermal expansion coefficient and crystal structure maintenance of stable compounds in those alloys.

关键词： 2NN MEAM Interatomic potential Mg-Al-Ca Mg-Al-Zn Atomistic simulation

A neural network model for high entropy alloy design

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npj Computational Materials 2023年第1期9卷 1734-1746页

作者： Jaemin Wang Hyeonseok Kwon Hyoung Seop Kim byeong-joo Lee Department of Materials Science and Engineering Pohang University of Science and Technology(POSTECH)Pohang 37673Republic of Korea Graduate Institute of Ferrous and Energy materials Technology(GIFT) Pohang University of Science and Technology(POSTECH)Pohang 37673Republic of Korea Center for Heterogenic Metal Additive Manufacturing Pohang University of Science and Technology(POSTECH)Pohang 37673Republic of Korea Institute for Convergence Research and Education in Advanced Technology Yonsei UniversitySeoul 03722Republic of Korea Advanced Institute for Materials Research(WPI-AIMR) Tohoku UniversitySendai 980-8577Japan

A neural network model is developed to search vast compositional space of high entropy alloys(HEAs).The model predicts the mechanical properties of HEAs better than several other ***’s because the special structure of the model helps the model understand the characteristics of constituent elements of *** addition,thermodynamics descriptors were utilized as input to the model so that the model predicts better by understanding the thermodynamic properties of HEAs.A conditional random search,which is good at finding local optimal values,was selected as the inverse predictor and designed two HEAs using the *** experimentally verified that the HEAs have the best combination of strength and ductility and this proves the validity of the model and alloy design *** strengthening mechanism of the designed HEAs is further discussed based on microstructure and lattice distortion *** present alloy design approach,specialized in finding multiple local optima,could help researchers design an infinite number of new alloys with interesting properties.

关键词： alloy alloys microstructure

Flow characteristics of aluminum coated boron steel in hot press forming

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中国有色金属学会会刊：英文版 2009年第4期19卷 913-916页

作者： Jeong-Hwan JANG Jae-Ho LEE Bye ong-don joo Young-Hoon MOON School of Mechanical Engineering Pusan National University

The flow characteristics of aluminum coated boron steel in hot press forming were ***,the effects of aluminum coated layer on press forming were analyzed during deep *** results show that aluminum coated boron steel exhibits a high sensitivity on temperature and strain *** coating layer appears in surface flaking in a temperature range of 700-800 ℃,but smooth surface is formed above 900 ℃.

关键词：热压成型流动特性铝涂层硼钢表面剥落温度范围冲压成形高灵敏度

Understanding the physical metallurgy of the CoCrFeMnNi high-entropy alloy:an atomistic simulation study

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npj Computational Materials 2018年第1期4卷 662-670页

作者： Won-Mi Choi Yong Hee Jo Seok Su Sohn Sunghak Lee byeong-joo Lee Department of Material Science and Engineering Pohang University of Science and Technology(POSTECH)Pohang 37673Republic of Korea

Although high-entropy alloys(HEAs)are attracting interest,the physical metallurgical mechanisms related to their properties have mostly not been clarified,and this limits wider industrial applications,in addition to the high alloy *** clarify the physical metallurgical reasons for the materials phenomena(sluggish diffusion and micro-twining at cryogenic temperatures)and investigate the effect of individual elements on solid solution hardening for the equiatomic CoCrFeMnNi HEA based on atomistic simulations(Monte Carlo,molecular dynamics and molecular statics).A significant number of stable vacant lattice sites with high migration energy barriers exists and is thought to cause the sluggish *** predict that the hexagonal close-packed(hcp)structure is more stable than the face-centered cubic(fcc)structure at 0 K,which we propose as the fundamental reason for the micro-twinning at cryogenic *** alloying effect on the critical resolved shear stress(CRSS)is well predicted by the atomistic simulation,used for a design of non-equiatomic fcc HEAs with improved strength,and is experimentally *** study demonstrates the applicability of the proposed atomistic approach combined with a thermodynamic calculation technique to a computational design of advanced HEAs.

关键词： alloy alloying entropy

Activation of non-basalslip in multicomponent Mg alloy

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Journal of Magnesium and Alloys 2022年第2期10卷 629-642页

作者： Hyo-Sun Jang Jong-Kwan Lee Antonio João Seco Ferreira Tapia Nack joon Kim byeong-joo Lee Department of Materials Science and Engineering Pohang University of Science and Technology(POSTECH)Pohang 37673Republic of Korea Graduate Institute of Ferrous Technology Pohang University of Science and Technology(POSTECH)Pohang 37673Republic of Korea

Activating non-basalslip is a key method to improve room temperature ductility and formability of Mg ***,the detailed criterion for activation of theslip in multicomponent Mg alloys,which can be utilized in commercial Mg alloys,requires further *** present authors investigated the mechanism and criterion using a molecular statics simulation on dislocation behaviors in multicomponent Mg *** found that if multicomponent Mg alloys have an equivalent dislocation binding intensity to associated binary Mg alloys that are optimized to minimize the critical resolved shear stress anisotropy and thus activate theslip,then the critical resolved shear stress anisotropy between slip systems of the multicomponent Mg alloys can also be minimized,resulting in activation of the*** activation is maximized in multicomponent Mg alloys when alloying a large amount of weak dislocation binding *** was confirmed through experiments that the multicomponent Mg alloys satisfying the above criterion show higher room-temperature tensile elongation and formability than other alloys.

关键词： Mg–Zn–Ca alloy Molecular statics simulation Ductility Formability

Modified embedded-atom interatomic potential for Co-W and Al-W systems

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Transactions of Nonferrous Metals Society of China 2015年第3期25卷 907-914页

作者：董卫平陈铮 byeong-joo LEE 浙江师范大学工学院金华321004 西北工业大学材料学院凝固国家重点实验室西安710072 Department of Materials Science and Engineering Division of Advanced Nuclear EngineeringPohang University of Science and Technology(POSTECH)Pohang 790-784Korea

A semi-empirical interatomic potential formalism,the second-nearest-neighbor modified embedded-atom method(2NN MEAM),has been applied to obtaining interatomic potentials for the Co-W and Al-W binary system using previously developed MEAM potentials of Co,Al and *** potential parameters were determined by fitting the experimental data on the enthalpy of formation,lattice parameter,melting point and elastic *** present potentials generally reproduce the fundamental physical properties of the Co-W and Al-W systems *** lattice parameters,the enthalpy of formation,the thermal stability and the elastic constants match well with experiment and the first-principles *** enthalpy of mixing and the enthalpy of formation and mixing of liquid are in good agreement with CALPHAD *** potentials can be easily combined with already-developed MEAM potentials for binary cobalt systems and can be used to describe Co-Al-W-based multicomponent alloys,especially for interfacial properties.

关键词： modified embedded-atom method Co-W system Al-W system atomistic simulation