梯度纳米结构金属的应变硬化行为及微观机理

项目名称： 梯度纳米结构金属的应变硬化行为及微观机理

项目编号： No.51301187

项目类型： 青年科学基金项目

立项/批准年度： 2014

项目学科： 一般工业技术

项目作者： 陈柳

作者单位： 中国科学院力学研究所

项目金额： 25万元

中文摘要： 利用表面机械研磨技术制备奥氏体不锈钢的梯度纳米结构块体样品，为揭示梯度纳米结构金属的应变硬化行为及微结构机理，进行拉伸、循环应力松弛和显微压入等力学性能测试，研究表层的强度和塑性等力学性能；利用有限元模拟，研究表层与粗晶基体塑性协调的微观力学过程；利用X射线衍射、透射电子显微镜等研究梯度纳米结构表层的晶粒尺寸、孪晶和相组成的梯度分布特征，重点关注不同拉伸应变下梯度纳米结构表层中位错、层错、孪晶和相变的形成、发生及交互作用，揭示(1)梯度纳米结构表层应变硬化的微结构机理；(2)表层与粗晶基体塑性协调的微观力学过程。通过本项目的研究，阐明梯度纳米结构金属高拉伸伸长率的微观机制，建立梯度纳米结构金属宏观力学性能与关键梯度参量的关联，为澄清纳米金属本征力学性能、突破纳米金属低塑性瓶颈提供思路。

中文关键词： 梯度纳米结构；塑性变形；应变硬化；力学性能；表面机械研磨

英文摘要： The GNS/CG (Gradient nanostructured/coarse grained) architecture is generated in austenitic stainless steel plates by means of surface mechanical attrition treatment (SMAT) to reveal the strain hardening behavior and inherent mechanism during tensile deformation. Mechanical properties are tested by quasi-static tensile, repeated stress-relaxation, and micro-indentation methods, upon which the related strength, ductility and strain hardening are analyzed. Meanwhile, Finite element analysis is used to research the micro-mechanical process of compatible deformation between GNS layers and coarse grained matrix.Furthermore, the gradient features of distribution for grain size,deformation twin, and martensite are characterized by X-ray diffraction, transmission electron microscope techniques and so on. Most importantly, close attention is paid to the formation, activation, and interaction of crystalline defects, such as dislocation, stacking fault,twin, and martensite. The results would reveal the micro-mechanical compatible deformation process occuring between GNS layers and coarse grained matrix, and uncover the inherent strain hardening mechanism of GNS/CG architecture resulting in extrordinary high tensile ductility. This proposal is aiming at elucidating the intrinsic tensile plasticity of nano-grained metals, an

英文关键词： Gradient structured；Plastic deformation；Strain hardening；Mechanical properties；Surface mechanically attrition treatment