Article
Nanoscience & Nanotechnology
I-An Su, Ko-Kai Tseng, Jien-Wei Yeh, Badr El-Sayed, Chia-Heng Liu, Shing-Hoa Wang
Summary: The metastable beta-type medium-entropy refractory alloy Hf20Nb10Ti35Zr35 was designed to have a ductile BCC structure in the as-solution-treated state and aged to achieve a combination of strength and ductility. The strengthening mechanisms, including transformation-induced plasticity, twinning-induced plasticity, and precipitation strengthening, serve as a basis for alloy design and improving the mechanical properties.
SCRIPTA MATERIALIA
(2022)
Article
Materials Science, Multidisciplinary
Guo-Dong Liu, Xue-Mei Luo, Ji-Peng Zou, Bin Zhang, Guang-Ping Zhang
Summary: The tensile tests of VCoNi medium-entropy alloy with different grain sizes were conducted at low temperatures. The results showed that the alloy exhibited a high grain boundary strengthening ability, which increased with decreasing temperature. This ability was significantly higher than that of other materials at room temperature. A new model was proposed to describe the high grain boundary strengthening ability, based on the intrinsic stacking fault energy and lattice friction stress. The high grain boundary strengthening ability of the VCoNi medium-entropy alloy was mainly attributed to its high lattice friction stress.
MATERIALS CHARACTERIZATION
(2023)
Review
Chemistry, Multidisciplinary
Hang Wang, Quanfeng He, Xiang Gao, Yinghui Shang, Wenqing Zhu, Weijiang Zhao, Zhaoqi Chen, Hao Gong, Yong Yang
Summary: Since 2004, the design of high entropy alloys (HEAs) has sparked significant interest in the materials science community due to their exceptional structural and functional properties. By incorporating multiple principal elements into a common lattice, a highly distorted lattice can be created, enabling HEAs to offer a promising combination of mechanical and physical properties that are not typically observed in conventional alloys. This article provides an extensive overview of multifunctional HEAs with severe lattice distortion, including theoretical models, experimental and computational methods, and the impact of lattice distortion on their mechanical, physical, and electrochemical properties. The review aims to stimulate further research into the study of distorted lattices in crystalline solids.
ADVANCED MATERIALS
(2023)
Article
Chemistry, Multidisciplinary
Dou Ning, Wenjie Lu, Xian Luo, Yanqing Yang, Bin Huang
Summary: In this study, a gradient nanostructure (GNS) was fabricated in an equiatomic CrCoNi medium-entropy alloy by high-energy shot peening (HESP). The microstructures of the GNS samples at different depths within the deformed layer were investigated in detail. The deformation process was mainly influenced by the interaction between dislocations and deformation twins due to the low stacking fault energy (SFE) of the alloy. The formation of the nanocrystalline structure involved three stages: coarse-grained deformation, ultrafine grain deformation, and nanocrystalline deformation.
Article
Metallurgy & Metallurgical Engineering
Oleg Sitdikov, Elena Avtokratova, Oksana Latypova, Michael Markushev
Summary: This study compared the structure and mechanical behavior of an Al-5Mg-0.18Mn-0.25c-0.08Zr-0.01Fe-0.01Si alloy under different deformation processes, showing that MIF resulted in ultrafine-grained structure and significantly enhanced strength and ductility after WR and CR. ECAP achieved more profound grain refinement but equal properties with MIF after WR, while CR following ECAP exhibited higher strengthening and slightly better superplastic behavior compared to MIF.
TRANSACTIONS OF NONFERROUS METALS SOCIETY OF CHINA
(2021)
Article
Chemistry, Physical
Hyeonseok Kwon, Peyman Asghari-Rad, Jeong Min Park, Praveen Sathiyamoorthi, Jae Wung Bae, Jongun Moon, Alireza Zargaran, Yeon Taek Choi, Sujung Son, Hyoung Seop Kim
Summary: A strategy to improve the tensile properties of Co17.5Cr12.5Fe55Ni10Mo5 medium-entropy alloy through high-pressure torsion and subsequent annealing was presented. The combination of grain refinement and precipitation contributed to excellent strength, while post-HPT annealing provided substantial ductility, resulting in a yield strength of 1 GPa with over 15% uniform elongation.
Review
Materials Science, Multidisciplinary
Pavel Dolzhenko, Marina Tikhonova, Marina Odnobokova, Rustam Kaibyshev, Andrey Belyakov
Summary: The aim of this review is to summarize recent achievements in the development of ultrafine-grained austenitic/ferritic stainless steels through large strain deformation. The paper discusses various methods of large strain deformation for producing ultrafine-grained metallic materials. It also explores the structural mechanisms responsible for grain refinement during plastic deformation and examines the physical and mechanical properties of ultrafine-grained stainless steels. The review concludes that the development of ultrafine-grained microstructures during severe plastic deformation is a result of continuous dynamic recrystallization, with the misorientations among strain-induced cells/subgrains progressively increasing.
Article
Chemistry, Physical
Yufang Zhao, Yaqiang Wang, Kai Wu, Jinyu Zhang, Gang Liu, Jun Sun
Summary: Introducing heterogeneous interfaces by constructing laminated structure is a promising approach to achieve controllable strengthening behavior of high entropy alloys. In this study, the microstructural evolution and mechanical properties of Ni/Fe50Mn30Co10Ni10 nanolaminates were systematically investigated. The nanoindentation hardness of the nanolaminates initially increased and then decreased with decreasing layer thickness, reaching a maximum value at around 25 nm. The transformation of constraining barrier for dislocation slipping from the heterogeneous interfaces to columnar grain boundaries was identified as the cause for this behavior. The interfacial structure transformed from incoherent to completely coherent below 25 nm, and both constituent layers contributed significantly to the plastic deformation. The h-dependent mechanical behavior can be explained by the co-deformation of constituent layers and the structural evolution of the interface.
JOURNAL OF ALLOYS AND COMPOUNDS
(2022)
Article
Materials Science, Multidisciplinary
Haoyuan Liu, Chang Gu, Kai Zhai, Chengduo Wang
Summary: We have developed a Co-free equiatomic FeCrNiMn alloy with high yield strength and elongation. By introducing novel networks composed of ultrafine precipitates and reducing coarse dendrites through annealing, the newly-developed medium entropy alloy exhibits superior mechanical properties compared to expensive FeCoNiCrMn high entropy alloys.
Article
Chemistry, Physical
Hyojin Park, Nhung Thi-Cam Nguyen, Praveen Sathiyamoorthi, Sujung Son, Jongun Moon, Hyoung Seop Kim
Summary: In this study, the superplastic behavior and microstructural characteristics of the high pressure torsion-processed Al-15(CuFeMn)(85) immiscible medium-entropy alloy (IMMEA) were investigated. The multi-phase structure generated through spinodal-like decomposition in IMMEA played a key role in maintaining the ultra-fine structure and preserving an equiaxed shape during testing at high temperatures, ultimately leading to superplastic behavior. This study is the first IMMEA superplasticity study and these results contribute to a better comprehension of the phenomenon.
Article
Materials Science, Multidisciplinary
O. Sitdikov, E. Avtokratova, M. Markushev
Summary: The study revealed that the grain refinement of Al-Mg-based alloy during multidirectional isothermal forging occurs through continuous dynamic recrystallization controlled by nanosized precipitates, resulting in the formation of (ultra) fine grain structure.
METALS AND MATERIALS INTERNATIONAL
(2021)
Article
Materials Science, Multidisciplinary
Gang Yao, William-Yi Wang, Pei-Xuan Li, Ke Ren, Jia-Qi Lu, Xing-Yu Gao, De-Ye Lin, Jun Wang, Yi-Guang Wang, Hai-Feng Song, Zi-Kui Liu, Jin-Shan Li
Summary: This study comprehensively investigates the effects of transition metals on high-entropy diborides (HEBs) and reveals the optimization mechanism of hardness based on the lattice distortion and electron contribution of transition metal atoms.
Article
Materials Science, Multidisciplinary
Zhaoyi Cheng, Jianrong Sun, Jinghao Cui, Da Chen, Junqiang Ren, Tao Wang, Hailong Chang, Pengfei Tai, Linqi Zhang, Yinan Tian, Yuting Wei, Jian Li
Summary: A mixed-strengthening-mechanism model dominated by precipitation and fine-grain strengthening is proposed to explain the increase in yield strength of FeCrV-based MEAs due to Ti addition. The Laves-phase precipitation formed by adding Ti improves the compressive plastic deformation through grain refinement, crack bridging, and crack deflection in MEAs. Moreover, the high thermal conductivity of FeCrVTix MEAs primarily results from the inelastic scattering of phonons and electrons in the medium/high-temperature regions.
MATERIALS CHARACTERIZATION
(2023)
Article
Chemistry, Multidisciplinary
Yanbin Wang, Feng Shi, Julien Gasc, Hiroaki Ohfuji, Bin Wen, Tony Yu, Timothy Officer, Norimasa Nishiyama, Toru Shinmei, Tetsuo Irifune
Summary: In the deformation process of NPD samples within the diamond stability field, it was found that deformation was not achieved through dislocation slip, but rather through the nucleation of dislocations and lattice gliding. In comparison to conventional polycrystalline diamond composites, NPD exhibits higher strength, which is attributed to defect-source strengthening and nanotwinning.
Article
Nanoscience & Nanotechnology
Jiaxiang Li, Kenta Yamanaka, Akihiko Chiba
Summary: By using thermodynamic and ab initio calculations, this study developed a non-equiatomic NiCoCrFe-based HEA with high Mo content and enhanced lattice distortion for solid-solution strengthening. The designed HEA exhibited a single fcc lattice and slight grain boundary segregation of excess Mo had negligible influence on lattice concentrations and solid-solution strengthening.
MATERIALS SCIENCE AND ENGINEERING A-STRUCTURAL MATERIALS PROPERTIES MICROSTRUCTURE AND PROCESSING
(2021)
Article
Materials Science, Multidisciplinary
Jongun Moon, Eun Seong Kim, Yeon Taek Choi, Ho-Joon Moon, Jung-Wook Cho, Hyoung Seop Kim
Summary: In this study, Zr was added to a cast Cu60Fe40 alloy to suppress liquid-liquid phase separation and improve the microstructure and mechanical properties. The addition of Zr successfully inhibits the phase separation, but leads to the formation of FeZr-rich precipitates, which enhances the strength and hardness of the alloy.
METALS AND MATERIALS INTERNATIONAL
(2023)
Article
Materials Science, Multidisciplinary
Yiming Yu, Yi Liu, Renlong Xiong, Tuanwei Zhang, Hanxin Chen, Hyoung Seop Kim
Summary: In this study, a new image processing method called Oriented-Linear Object Segmentation (OLOS) was proposed for measuring the volume fraction of mechanical twins in transmission electron microscopy (TEM) images. The results showed that this OLOS method allows for a more direct, rapid, and effective measurement of twin volume fractions in TEM images. It has potential applications in quantifying the twinning-induced plasticity (TWIP) effect in various metals, including TWIP steels, high entropy alloys, and copper.
MATERIALS CHARACTERIZATION
(2023)
Article
Nanoscience & Nanotechnology
Jungwan Lee, Jeong Min Park, Jongun Moon, Hyojin Park, Hyoung Seop Kim
Summary: Impact toughness at ambient and cryogenic temperatures was investigated for CuFeMn and Al15(CuFeMn)85 immiscible medium-entropy alloys. These alloys exhibited different impact toughness behavior at different temperatures and showed higher impact toughness values compared to dual-phase steels with similar strength levels.
MATERIALS SCIENCE AND ENGINEERING A-STRUCTURAL MATERIALS PROPERTIES MICROSTRUCTURE AND PROCESSING
(2023)
Article
Materials Science, Multidisciplinary
Jeong Ah Lee, Man Jae Sagong, Jaimyun Jung, Eun Seong Kim, Hyoung Seop Kim
Summary: Recently, there has been development in metal additive manufacturing (MAM) due to its advantages such as complex geometries, waste reduction, design flexibility, and cost-effectiveness. However, the influence of processing parameters on MAM product properties is not well understood or easily predictable. This study applies explainable machine learning (xML) models to predict and understand the geometry and defects of MAM-processed Fe-Ni alloys. Gaussian process regression (GPR) predicts as-printed height and porosity, while a support vector machine (SVM) classifies defect types based on predicted and measured porosities. The Shapley additive explanation (SHAP) approach is used to analyze feature importance. This study provides insights into the use of xML models to link processing with results in MAM.
JOURNAL OF MATERIALS RESEARCH AND TECHNOLOGY-JMR&T
(2023)
Article
Materials Science, Multidisciplinary
Sujung Son, Jaeik Kwak, Farahnaz Haftlang, Hyeonseok Kwon, Yong-Tae Kim, Sunghak Lee, Hyoung Seop Kim
Summary: The corrosion properties and passivation layer of VCrFeCoNi medium-entropy alloy (V-MEA) were investigated in this study. The V-MEA exhibited a corrosion current density of -0.101 mA and a corrosion potential of -0.336 V, with a broad passivation region of -0.763 V. The V-MEA showed a multilayer passivation with a vanadium oxides-rich outer layer and a chromium oxide-rich inner layer. The outer layer acted as a cation-selective layer to prevent Cl- ions, while the inner layer acted as an anion-selective species to capture the Cl- ions. As a result, fewer Cl- ions could penetrate the passivation layer, leading to the broad passivation region of the V-MEA.
JOURNAL OF MATERIALS RESEARCH AND TECHNOLOGY-JMR&T
(2023)
Article
Materials Science, Multidisciplinary
Hyeonseok Kwon, Praveen Sathiyamoorthi, Manogna Karthik Gangaraju, Alireza Zargaran, Jaemin Wang, Yoon-Uk Heo, Stefanus Harjo, Wu Gong, Byeong-Joo Lee, Hyoung Seop Kim
Summary: In this work, a novel Fe-based medium-entropy alloy was designed based on the characteristics of maraging steels. By a single-step aging at 650 celcius for 10 min, the alloy exhibited microstructures consisting of high-density nanoprecipitates and reverted FCC phase, resulting in ultrahigh yield strength and good ductility.
Article
Materials Science, Multidisciplinary
Jihye Kwon, Olivier Bouaziz, Hyoung Seop Kim, Yuri Estrin
Summary: Crumpled metallic thin foils have great potential as weight-saving and energy-absorption materials, but further research is needed on their crumpling process and mechanical behavior, considering their complex internal structures. This study presents two possible computational strategies for simulating crumpled materials under closed-die compression. The analysis shows that the continuum-based approach is more suitable for representing the macroscopic mechanical behavior of crumpled materials within a certain range of relative densities. The porous continuum approach also offers the benefits of low computational cost and high efficacy. However, the direct method is preferable when accurately reproducing internal structural pattern changes is necessary, such as for predicting mechanical response under complex loading conditions.
ADVANCED ENGINEERING MATERIALS
(2023)
Article
Materials Science, Multidisciplinary
Jeong Ah Lee, Jaejung Park, Yeon Taek Choi, Rae Eon Kim, Jaimyun Jung, Seungchul Lee, Min Hong Seo, Hyoung Seop Kim
Summary: This study utilizes a machine learning framework coupled with imputation methods to augment the collected experimental data and predicts the hole expansion ratio. The influences of various tensile properties on the hole expansion ratio were quantitatively determined for the first time through machine learning and analyzed using explainable artificial intelligence techniques.
JOURNAL OF MATERIALS SCIENCE
(2023)
Article
Materials Science, Multidisciplinary
Zhiqin Yang, Jianxing Bao, Chaogang Ding, Sujung Son, Zhiliang Ning, Jie Xu, Debin Shan, Bin Guo, Hyoung Seop Kim
Summary: Electrically assisted deformation (EAD) is used to improve the formability and prevent cracking in the processing of Al0.6CoCrFeNiMn high entropy alloy (HEA) at room temperature. The study systematically investigates the electroplasticity of the HEA through electrically assisted uniaxial tension. Results show that pulse current increases sample temperature and enhances flow stress and elongation. This study confirms that EAD effectively improves the formability of HEAs and provides guidance for their component forming.
JOURNAL OF MATERIALS SCIENCE & TECHNOLOGY
(2023)
Article
Materials Science, Multidisciplinary
D. H. Chung, J. Lee, Q. F. He, Y. K. Kim, K. R. Lim, H. S. Kim, Y. Yang, Y. S. Na
Summary: The study investigates the toughening/strengthening mechanisms of heterostructured eutectic high-entropy alloys (EHEAs) and discovers that fully eutectic HEAs show superior performance in both yield stress and fracture toughness due to the high hetero-deformation-induced (HDI) strengthening/toughening associated with a high misorientation angle at the grain/phase boundaries.
JOURNAL OF MATERIALS SCIENCE & TECHNOLOGY
(2023)
Article
Nanoscience & Nanotechnology
Jiajia Shen, J. G. Lopes, Zhi Zeng, Yeon Taek Choi, E. Maawad, N. Schell, Hyoung Seop Kim, Rajiv S. Mishra, J. P. Oliveira
Summary: High energy synchrotron X-ray diffraction was utilized to investigate the deformation behavior of an as-cast eutectic AlCoCrFeNi2.1 high entropy alloy during tensile testing. The study determined the volume fractions of different phases and elucidated their roles in the alloy's mechanical response. The findings showed that stress partitioning between the soft disordered FCC and hard ordered B2 BCC phases could modulate the material's deformation behavior. Additionally, analysis of dislocation density and lattice strain demonstrated the preferential deformation of certain lattice planes and the significance of the B2 BCC phase in strengthening the alloy.
MATERIALS SCIENCE AND ENGINEERING A-STRUCTURAL MATERIALS PROPERTIES MICROSTRUCTURE AND PROCESSING
(2023)
Article
Medicine, General & Internal
Dougho Park, Chan Woong Jang, Han Eol Cho, Jong Hun Kim, Hyoung Seop Kim
Summary: In South Korea's Long-Term Care Insurance (LTCI) system, the special dementia rating (SDR) is a registration grading for dementia patients without physical disability or functional restrictions, and it is the first applicable registration after diagnosis. This study investigated the relationship between educational level and residential area with the age of SDR registration and dementia diagnosis. The results showed that lower education level and rural residency were associated with older age at diagnosis and SDR registration, while higher education level and urban residency were associated with younger age at diagnosis and SDR registration. This suggests that cognitive decline sensitivity and medical accessibility play a role in the early diagnosis and registration of dementia.
Article
Materials Science, Multidisciplinary
K. R. Ramkumar, Srinivasan Arthanari, Sivakumar Bose, Sang Guk Jeong, S. Sivasankaran, Huseung Lee, Hyoung Seop Kim
Summary: This study developed Al2O3 reinforced alpha-brass nanocomposites using spark plasma sintering and evaluated their electrochemical properties in a corrosive solution. The results showed that the uniformly dispersed Al2O3 particles in 3 wt.% Al2O3 nanocomposites reduced galvanic coupling, resulting in improved corrosion resistance and passivation behavior.
Article
Chemistry, Physical
Amin Radi, Canay Isil, S. Vegar Seyedmohammadi, Hyoung Seop Kim, Guney Guven Yapici
Summary: This study investigates the influence of secondary phases and dislocation substructures in high entropy alloys (HEAs) and achieves exceptional mechanical properties by controlling microstructure, grain size, and dislocation substructure. The results highlight the importance of grain size in facilitating the generation of necessary dislocations during plastic deformation.
JOURNAL OF ALLOYS AND COMPOUNDS
(2023)
Article
Materials Science, Multidisciplinary
Hamed Shahmir, Shabnam Kazemi, Mohammad Sajad Mehranpour, Hyoung Seop Kim
Summary: The effect of Al addition on the microstructure of a CoCrFeNiMn high-entropy alloy was investigated using a novel approach. The formation and stability of phases were examined through heat treatment and CALPHAD predictions. This method is significant for alloy design as it allows for a quick study of phase evolution in complex multi-component alloys.
MATERIALS TODAY COMMUNICATIONS
(2023)
