超高强、高韧α+β型钛合金的电致强化机理研究

This project originating from the urgent demands for the high performance of Ti alloy in aerospace industry, breaks the conventional process limitation on the strength and toughness improvement in the most widely used Ti-6Al-4V (TC4) alloy, and overcomes the difficulty in achieving the ultra-high strength Ti alloy with enough ductility. The innovation of this project is beginning with investigating the normal/inverse phase transformation, recrystallization, solid-solution/aged precipitation, metastable phase formation, etc. in the α+β Ti alloy via electropulsing treatment (EPT). Moreover, the work will reveal the evolution law of Ti alloy microstructure under the extreme non-equilibrium condition induced by the effect of instantaneous high-energy multi-field coupling, and illuminate the electro-strengthening mechanism of the Ti alloy. Through controlling the constrained force and the environment temperature, find out the intrinsic relationship of the single physical field and the electro-strengthening mechanism in the Ti alloy. Based on the interaction of the instantaneous various strengthening effects when the high-energy electropulsing flows through the constrained solid metal, combining with the enforced constraints induced by electric heating expansion, heating and cooling control technology, through optimizing the EPT parameters to control the size, morphology, distribution and composition ratio, finally, obtain the ultra-high strength Ti alloy with enough plasticity and toughness. This study will provide reference and theoretical basis for realizing the ultra-high strengthening and toughing via using EPT in Ti alloy.

本项目针对航空航天工业中钛合金高性能化的迫切需求，突破传统方法对使用最为广泛的Ti-6Al-4V（TC4）合金强韧性提高的限制，从而解决在保持足够塑韧性的前提下实现合金超高强化的难题。创新思路在于以α+β型钛合金为基础材料，从电-热-力多场耦合作用引发的合金中正/逆相变、再结晶、固溶/时效析出、亚稳相形成等非常规变化入手，揭示极端非平衡条件下钛合金微观组织结构演变规律，阐述钛合金的电致强化机理。通过控制约束力及环境温度，揭示单一物理场与钛合金强韧化机制的本征关系。基于高能量脉冲电流通过有约束的固态金属产生的瞬时多强化效应的交互作用，配合电热膨胀强制约束和控热控冷技术，优化脉冲电流处理参数，调控组织中多相尺寸、形态、分布及组成比例，在保持足够塑、韧性的前提下实现钛合金的超高强度化。为利用脉冲电流处理实现钛合金超高强韧化提供借鉴及理论基础。

本项目针对航空航天工业中钛合金高性能化的迫切需求，突破了传统方法对应用最为广泛的TC4钛合金强韧性提高的限制，解决了在保持足够塑性前提下实现材料超高强化的难题。研究表明：通过脉冲电流处理与传统热处理结合可以实现钛合金材料的高强韧化（抗拉强度≥1300MPa，延伸率≥13%）。材料的高性能得益于脉冲电流处理过程中由于形核能垒下降而导致的晶粒细化，并且在快速相变过程中更多的细小β相也得以保留，同时材料中的织构弱化，这些作用使得材料不仅强度提高而且塑性并不损失。本项目利用脉冲电流引发的快速相变过程实现了调控钛合金材料的组织与性能，不但扩大了此技术的应用领域，而且揭示了α+β型钛合金材料强韧化的机理，为此类具有同素异构转变的合金组织与性能调控提供了新的方法和思路。