异构金属材料及其塑性变形与应变硬化

Heterostructured Metallic Materials:Plastic Deformation and Strain Hardening

金属材料异构(heterostructure)是将具有显著流变应力差异的软硬相间区域作为基元进行有序构筑而成的微观组织,是旨在提高应变硬化能力和拉伸塑性的微结构设计策略,迄今应用于各种金属结构材料并获得了强度与塑性/韧性等力学性能的优异匹配。异构策略的出发点是其特征的力学响应,即塑性变形时在异构基元界面形成的应变梯度,异构的特征应力应变响应是力学迟滞环。相比均质结构中主导的林位错塑性和林硬化,异构为了协调界面应变梯度而产生几何必需位错,新增了基于几何必需位错的异质塑性变形并引起额外的应变硬化与额外的强化。本文综述了近期异构金属材料的研究进展,首先定义了异构中基元并据此把异构分类为基元异构、亚基元异构以及复合异构,随后分析并讨论了异构塑性变形时界面和位错等微结构演化,以及异质塑性变形、应变硬化和强化行为,最后展望了异构提升宏观力学性能匹配的潜力。

Strong and tough metallic materials are desired for light-weight structural applications in transportation and aerospace industries.Recently,heterostructures have been found to possess unprecedented strength-and-ductility synergy,which is until now considered impossible to achieve.Heterostructured metallic materials comprise heterogeneous zones with dramatic variations(> 100%) particularly in mechanical properties.The interaction in these hetero-zones produces a synergistic effect wherein the integrated property exceeds the prediction by the rule-of-mixtures.More importantly,the heterostructured materials can be produced by current industrial facilities at large scale and low cost.The superior properties of heterostructured materials are attributed to the heterodeformation induced(HDI) strengthening and strain hardening,which is produced by the piling-up of geometrically necessary dislocations(GNDs).These GNDs are needed to accommodate the strain gradient near hetero-zone boundaries,across which there is high mechanical incompatibility and strain partitioning.This paper classifies the types of heterostructures and delineates the deformation behavior and mechanisms of heterostructured materials.