http://chineseinput.net/에서 pinyin(병음)방식으로 중국어를 변환할 수 있습니다.
변환된 중국어를 복사하여 사용하시면 됩니다.
Asghari-Rad, Peyman,Kim, Yongju,Nguyen, Nhung Thi-Cam,Kim, Hyoung Seop The Korean Powder Metallurgy Institute 2020 한국분말재료학회지 (KPMI) Vol.27 No.1
In this research, a new medium-entropy alloy with an equiatomic composition of FeCuNi was designed using a phase diagram (CALPHAD) technique. The FeCuNi MEA was produced from pure iron, copper, and nickel powders through mechanical alloying. The alloy powders were consolidated via a high-pressure torsion process to obtain a rigid bulk specimen. Subsequently, annealing treatment at different conditions was conducted on the four turn HPT-processed specimen. The microstructural analysis indicates that an ultrafine-grained microstructure is achieved after post-HPT annealing, and microstructural evolutions at various stages of processing were consistent with the thermodynamic calculations. The results indicate that the post-HPT-annealed microstructure consists of a dual-phase structure with two FCC phases: one rich in Cu and the other rich in Fe and Ni. The kernel average misorientation value decreases with the increase in the annealing time and temperature, indicating the recovery of HPT-induced dislocations.
Asghari-Rad, Peyman,Choi, Yeon Taek,Nguyen, Nhung Thi-Cam,Sathiyamoorthi, Praveen,Kim, Hyoung Seop The Korean Powder MetallurgyMaterials Institute 2021 한국분말재료학회지 (KPMI) Vol.28 No.4
In this study, the layered structures of immiscible Fe and Cu metals were employed to investigate the interface evolution through solid-state mixing. The pure Fe and Cu powders were cold-consolidated by high-pressure torsion (HPT) to fabricate a layered Cu-Fe-Cu structure. The microstructural evolutions and flow of immiscible Fe and Cu metals were investigated following different iterations of HPT processing. The results indicate that the HPT-processed sample following four iterations showed a sharp chemical boundary between the Fe and Cu layers. In addition, the Cu powders exhibited perfect consolidation through HPT processing. However, the Fe layer contained many microcracks. After 20 iterations of HPT, the shear strain generated by HPT produced interface instability, which caused the initial layered structure to disappear.
Asghari-Rad, Peyman,Sathiyamoorthi, Praveen,Bae, Jae Wung,Moon, Jongun,Park, Jeong Min,Zargaran, Alireza,Kim, Hyoung Seop Elsevier 2019 Materials science & engineering. properties, micro Vol.744 No.-
<P><B>Abstract</B></P> <P>In the present study, V<SUB>10</SUB>Cr<SUB>15</SUB>Mn<SUB>5</SUB>Fe<SUB>35</SUB>Co<SUB>10</SUB>Ni<SUB>25</SUB> (at%) high-entropy alloy (HEA) of a single phase face-centered cubic structure with various grain sizes was fabricated. The influences of grain size on the work-hardening behavior and deformation mechanisms were investigated. The fine-grained and coarse-grained samples showed different work hardening behaviors during room temperature tensile deformation. Microstructural analysis revealed the presence of a high-density tangled dislocation structure without any mechanical twinning in the fine-grained sample, while mechanical twinning was observed to be the additional deformation mechanism in the coarse-grained sample.</P>
Fine tuning of tensile properties in CrCoNi medium entropy alloy through cold rolling and annealing
Sathiyamoorthi, Praveen,Asghari-Rad, Peyman,Bae, Jae Wung,Kim, Hyoung Seop Elsevier 2019 Intermetallics Vol.113 No.-
<P><B>Abstract</B></P> <P>In the present study, tensile properties of CrCoNi medium entropy alloy with different microstructures (recovery, partial recrystallization, recrystallization) were investigated by subjecting cold-rolled samples to different annealing conditions. The microstructure of the cold-rolled sample showed the presence of severely deformed grains with several deformation twins. Annealing of the cold-rolled samples at 700 °C and above for 60 min led to fully recrystallized microstructure, while annealing at temperatures lower than 700 °C led to recovery and partially recrystallized microstructures. The annealed samples showed a typical strength-ductility trade-off with an increasing fraction of recrystallized grains and increasing average grain size in samples with partially recrystallized and fully recrystallized microstructure, respectively. Fine tuning of microstructure led to a remarkable combination of strength (~1 GPa) and uniform elongation (28%) in the sample with partially recrystallized microstructure, which consists of ~77% of recrystallized grains with an average recrystallized grain size of ~3 μm.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Fine tuning of microstructure through cold rolling and annealing. </LI> <LI> A reasonable ductility requires minimum of 55% of recrystallized grains. </LI> <LI> Optimal tensile properties achieved in sample with 77% recrystallized grains. </LI> <LI> Combination of strengthening from back stress and Hall-Petch effect. </LI> </UL> </P>
Praveen, S.,Bae, Jae Wung,Asghari-Rad, Peyman,Park, Jeong Min,Kim, Hyoung Seop Elsevier 2018 Materials science & engineering. properties, micro Vol.735 No.-
<P><B>Abstract</B></P> <P>A nanocrystalline CoCrNi alloy of ~50 nm grain size with the ultra-high ultimate tensile strength of ~2.2 GPa and fracture strain of ~9% was fabricated using high-pressure torsion. The presence of high density of nano-twins, stacking faults, dislocations, and nano-grains is attributed to the superior mechanical properties.</P>
Yongju Kim,Hyung Keun Park,Peyman Asghari‑Rad,Jaimyun Jung,Jongun Moon,Hyoung Seop Kim 대한금속·재료학회 2021 METALS AND MATERIALS International Vol.27 No.7
Constitutive modeling of CoCrFeMnNi high-entropy alloy (HEA) at cryogenic temperature (77 K) and room temperature(293 K) has been investigated. The effect of temperature on deformation behavior such as twinning, forest hardening, andback stress hardening has been established. The enhanced ductility and strength of CoCrFeMnNi HEA at 77 K are duethe combination of sub-grain structure, twinning, and dislocations. This phenomenon is explained in terms of quantitativevalues of twin volume fraction, inter-twin spacing, and dislocation density. The isotropic kinematic constitutive model isconstructed with a critical twinning stress parameter to obtain the criteria for twinning initiation. The developed finite elementmodel simulation results at 77 K and 293 K are in good agreement with the experimental data. The model displays asmooth increase in the twin volume fraction until fracture point (maximum twin fraction region). Also, different modelingparameters are obtained for each temperature to account for the changing deformation behavior.
Sathiyamoorthi, Praveen,Moon, Jongun,Bae, Jae Wung,Asghari-Rad, Peyman,Kim, Hyoung Seop Elsevier 2019 Scripta materialia Vol.163 No.-
<P><B>Abstract</B></P> <P>Ultrafine-grained materials with nanotwins are expected to produce a remarkable combination of strength and ductility. In the present study, ultrafine-grained CoCrNi medium-entropy alloy with nanotwins is fabricated by high-pressure torsion followed by annealing; and investigated for cryogenic tensile properties. The alloy exhibits superior cryogenic tensile properties with a tensile strength of ~2 GPa and tensile strain of ~27%. The cryogenic tensile strength of ultrafine-grained sample increased by 67% as compared to the cryogenic tensile strength of coarse-grained sample due to fine grain size, annealing nanotwins, residual dislocation density, and strong temperature dependence of yield strength.</P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>