钛合金高温短时蠕变与应力松弛的关系研究*

蠕变或应力松弛被认为是钛合金板材热成形降低回弹的主要机理。目前对热校形阶段中的蠕变与应力松弛的区别及联系尚缺乏深入研究。本文主要进行了钛合金高温短时蠕变及应力松弛实验, 利用TEM对实验后的显微组织进行了观察。分别研究了温度、应力及时间对蠕变和应力松弛行为的影响规律, 从蠕变率-时间和蠕变-时间角度建立了蠕变与应力松弛之间的联系。研究表明: 钛合金在低温低应力下蠕变以原子扩散为主, 高温高应力下以位错滑移和攀移为主, 而应力松弛在不同温度时均以位错攀移为主要变形机制, 基于蠕变数据预测的应力松弛行为与实验结果符合较好。

Relation between Short-term Creep and Stress Relaxation of Titanium Alloy at High Temperature

Creep or stress relaxation is considered as a main mechanism of reducing the springback of titanium alloy sheet during thermal forming process. So far, the difference and relation between the two phenomena have not been clearly explored. In this paper, tests of short term creep and stress relaxation of Ti6Al4V alloy were conducted at high temperature. The microstructure of the tested alloy was observed by using TEM. Effects of temperature, stress and time on creep and stress relaxation behavior were studied, respectively. The correlation and difference between the two phenomena were compared based on relations of creep strain - time and strain rate - time. Results show that creep behavior is controlled by atom diffusion at low temperature under low stress; by dislocation slide and climb at high temperature under high stress. The stress relaxation behavior is mainly governed by dislocation climb. The predicted stress relaxation behavior based on the creep data shows a good agreement with the experiment.