纳米孪晶和梯度纳米结构金属强韧特性研究进展

金属材料在航空、航天工业以及民用工业等领域具有广泛的应用,如何获取同时具备高强度和良好塑性的金属材料一直是材料、物理、力学等不同学科长期以来亟待解决的难题.传统的强化方法包括应变强化、固溶强化、相变强化、晶粒细化强化和第二相弥散强化等,均会使材料的韧性或塑性降低.近年来,实验研究发现通过界面设计和微结构调控来可以制备出高强高韧的金属材料,认为位错与各类界面的相互作用、以及微结构优化对应力集中的削弱是材料强化和韧化的主要原因.根据已有实验观察,人们通过原子尺度方法定量分析高强高韧金属材料的变形机理,揭示其强化和韧化机制;同时,发展出基于变形机理的理论模型和有限元方法定量描述高强高韧金属的力学行为.论文将重点介绍纳米孪晶金属和梯度纳米结构金属的强韧特性研究进展,并对新型纳米结构金属材料的强韧特性优化进行展望.

Strength and Toughness Properties in Nanotwinned Metals and Gradient-nanostructured Metals: A Review

Metallic materials have been widely used in aviation, aerospace and civil industries. To achieve a metallic material with high yield strength and good ductility has become an important issue in the disciplines of materials, physics and mechanics. The traditional strengthening methods, such as strain hardening, solid-solution alloying, phase transformation, grain refinement, and second-phase dispersion strengthening, although can improve the strength, would greatly weaken the plastic properties. In recent years, experimental studies have demonstrated that interface design and microstructural control enable the metallic materials to be prepared with a good combination of high yield strength and high ductility. It has been proved that the interactions between the dislocations and various interfaces and the weakened stress concentration through the optimization of microstructures are the primary mechanisms of strengthening and toughening. On the basis of experimental observations, researchers applied the atomic methods to analyze the plastic deformation in the metallic materials with high strength and high ductility quantitatively, and gave insights into the strengthening mechanisms and failure behaviors. On the other hand, the mechanism-based theoretical model and the finite element approach were developed to describe the mechanical behaviors of novel metallic materials with excellent mechanical properties. In this work, we review the experimental and theoretical studies on the mechanical properties such as strength and ductility, and plastic deformations of nanotwinned metals and gradient-nanostructured metals; and put forward the prospect of optimization of high yield strength and high ductility for novel nanostructured metals.