针对超细晶Ti-6Al-4V钛合金塑性差，影响其服役性能的问题，本项目拟采用多向等温锻造技术，结合多级热处理工艺，利用钛合金中马氏体相变α´→(α+β)的细晶效应，在Ti-6Al-4V钛合金中获得超细晶等轴组织与片层粗晶组织共存的异构组织，从而制备出同时具有超细晶高强度和粗晶大塑性的大尺寸高强塑性Ti-6Al-4V钛合金。研究Ti-6Al-4V钛合金中α´马氏体相在热-力耦合作用下的相变细晶行为，探究Ti-6Al-4V钛合金在多向等温锻造过程中的非均匀组织形成机制以及热处理过程中变形组织的回复再结晶行为，明晰Ti-6Al-4V钛合金中超细晶等轴组织与片层粗晶组织共存的异构组织形成机理，探讨背应力强化及应变强化对材料塑性提升的作用机理，揭示异构组织材料的塑性提升机制，该项目的研究对于促进钛合金在我国航空航天工业中的应用具有重要意义。

Ultrafine-grained Ti-6Al-4V alloy possesses superior strength but low ductility, which severely limits its practical use. Thus, this project aims to achieve superior strength and good ductility in a Ti-6Al-4V alloy by introducing a novel microstructure consisting micrograined lamella embedded in an ultrafine-grained sphere matrix using multidirectional isothermal forging and multistage heat treatment. The martensitic phase transformation of α´→(α+β) under hot compression is used to achieve the ultrafine grains, and the phase transformation mechanisms will be studied. The microstructure evolution and phase transformation during multidirectional isothermal forging will be studied, and the dynamic recovery and dynamic recrystallization of deformed microstructure during the heat treatment will be investigated. The formation mechanism of heterostructured microstructure of micrograined lamella embedded in ultrafine-grained sphere matrix is to be clarified. The contributions of back stress strengthening and strain hardening to ductility improvement are to be understood. The mechanism of enhancement of ductility is to be revealed. This project has important implications for the promotion of titanium alloy in China’s aerospace industry.