Unveiling the grain boundary-related effects on the incipient plasticity and dislocation behavior in nanocrystalline CrCoNi medium-entropy alloy

作     者：Shuo Sun Yang Yang Chenxu Han Guixun Sun Yan Chen Hongxiang Zong Jiangjiang Hu Shuang Han Xiaozhou Liao Xiangdong Ding Jianshe Lian Shuo Sun;Yang Yang;Chenxu Han;Guixun Sun;Yan Chen;Hongxiang Zong;Jiangjiang Hu;Shuang Han;Xiaozhou Liao;Xiangdong Ding;Jianshe Lian

作者机构：Key Laboratory of Automobile MaterialsMinistry of EducationCollege of Materials Science and EngineeringJilin UniversityChangchun 130025China State Key Laboratory for Mechanical Behavior of MaterialsXi’an Jiaotong UniversityXi’an 710049China College of Mechanical EngineeringZhejiang University of TechnologyHangzhou 310014China School of AerospaceMechanical and Mechatronic EngineeringThe University of SydneySydneyNSW 2006Australia 

出 版 物：《Journal of Materials Science & Technology》 (材料科学技术（英文版）)

年 卷 期：2022年第127卷第32期

页      面：98-107页

核心收录：

学科分类：08[工学] 0805[工学-材料科学与工程（可授工学、理学学位）] 080502[工学-材料学] 0703[理学-化学] 

基　　金：the National Natural Science Foundation of China(Nos.51601067 and 51801184) the Zhejiang Public Welfare Technology Research Program(No.LGC21E010001) the Science and Technology Development Program of Jilin Province(No.20160520007JH) the Program for Jilin University Science and Technology Innovative Research Team(JLUSTIRT,2017TD-09)。 

主　　题：Medium-entropy alloy Nanocrystalline Nanoindentation Incipient plasticity Grain boundary 

摘      要：The incipient plasticity and dislocation behavior in a nanocrystalline(NC)CrCoNi medium-entropy alloy were systematically investigated in terms of pop-in events during instrumental nano-indentation tests.Quantitative statistical analysis and molecular dynamic simulations were performed to reveal the effects of grain boundaries(GBs)on initial stages of plastic deformation.Multiple pop-in events appeared during loading on the NC CrCoNi.The first pop-in that represents the initial yielding was identified to be controlled by dislocation nucleation,which is in sharp contrast to the continuous elastic-plastic transition mediated by GB mechanisms in NC pure metals.This can be attributed to the sluggish kinetics of the chemically complex GBs(CCGBs)in the NC CrCoNi that hinders diffusive GB activities but facilitates dislocation nucleation.Subsequent pop-ins were also found to be closely related to the extra dragging effects imposed by the CCGBs on dislocation propagation in the NC alloy.Moreover,the extremely small grain sizes and the consequent high-volume fraction of GBs in the NC alloy severely restrict the lengths of dislocation source and the radii of dislocation loop,giving rise to a higher critical stress,smaller activation volume and lower pop-in width as compared with its coarse-grained counterpart.These results provide new insights into the onset of nano-plasticity in concentrated multi-principal element alloys.