百纳米以下压入硬度规律的科学意义和挑战  

The significance and challenges on determining the size-effect of indentation hardness at nano-scale

作　　者：杨荣[1,2] 张泰华 肖攀 王军 张群[1,2,4] 双飞 柯孚久 白以龙 YANG Rong;ZHANG TaiHua;XIAO Pan;WANG Jun;ZHANG Qun;SHUANG Fei;KE FuJiu;BAI YiLong(State Key Laboratory of Nonlinear Mechanics,Institute of Mechanics,Chinese Academy of Sciences,Beijing 100190,China 2.School of Engineering Sciences,University of Chinese Academy of Sciences,Beijing 100049,China;3.College of Mechanical Engineering,Zhejiang University of Technology,Hangzhou 310014,Chin;4.Beij＇ing Institute of Structure and Environment Engineering,Beijing 100076,Chin;5.School of Physics and Nuclear Energy Engineering,Beihang University,Beijing 100191,China)

机构地区：[1]中国科学院力学研究所非线性力学国家重点实验室,北京100190 [2]中国科学院大学工程科学学院,北京100049 [3]浙江工业大学机械工程学院,杭州310014 [4]北京强度环境研究所,北京100076 [5]北京航空航天大学物理与核能工程学院,北京100191

出　　处：《中国科学：物理学、力学、天文学》2018年第9期14-22,共9页Scientia Sinica Physica,Mechanica & Astronomica

基　　金：国家自然科学基金(编号:11727803;11172305;11432014);国家重大科学研究计划(编号:2012CB937500);中国科学院战略性先导科技专项B类(编号:XDB22000000)资助项目

摘　　要：仪器化压入是广泛应用的微/纳米力学测试方法,可靠的百纳米以下压入硬度尺寸效应的规律及其机理是其中尚未完全认识清楚的问题.本文总结了课题组近期在百纳米以下压入硬度的实验和模拟方面的进展:通过精确控制试样晶向状态和表面粗糙度,表征压头尖端曲率,在大规模分子模拟中引入压头曲率参数,实现了实验和模拟的衔接和相互校核,获得了可靠的百纳米以下的压入硬度规律,并揭示了两种相反的尺寸效应的机理,即常规的随压入深度减小而增大的硬度尺寸效应来源于压头下方材料中位错的形核和传播,而与压入初始阶段的相反尺寸效应来源于压头尖端曲率和材料弹性行为之间的耦合效应;针对压入过程中的位错演化,系统对比了分子动力学和分子静力学的结果可靠性和计算效率与弛豫时间和能量收敛精度参数的关系,提出了选取模拟方法和模拟参数的依据.Instrumented indentation is a method that has been widely used to obtain material properties at micro and nano scale, yet creditable indentation size effect at real nano-scale and its mechanism are still unsolved. This paper summarizes our recent work on progresses in experimental and simulation approaches to this problem. By confirming the crystalline orientations and the surface roughness of the sample, obtaining the tip radius of the indenters, as well as considering tip radius in large-scale molecular simulation, the gap between the experiment and simulation results is bridged, and these two results can be cross verified with each other, which leads to a reliable hardness trend over the indentation depth at nano-scale. Two opposite size effects are observed, and their different mechanisms are revealed, as the conventional size effect results from the plastic behavior such as dislocation nucleation and propagation in the sample beneath the indenter, while the initial reverse size effect is due to the combined effect of the indenter roundness and elastic behavior of the material. Systematic investigation on the efficiency and fidelity of MD and MS is carried out, on problem of the dislocation evolution during indentation, the influence of the relaxation time and convergence resolution on the load curve and dislocation patterns are studied, and suggestion on choice of two simulation methods and the relaxation time and convergence resolution are given.

关 键 词：纳米压入 压入硬度 尺寸效应 位错 计算效率 

分 类 号：TB302.3[一般工业技术—材料科学与工程]