Ti6Al4V合金的高温短时蠕变本构关系与应力松弛行为

Short-term creep constitutive relation and stress relaxation behavior of Ti6Al4V alloy at high temperature

对Ti6Al4V合金在不同温度(650、700和750℃)、初始应力(100和150 MPa)和预应变(3.97%和15.87%)条件下进行多组应力松弛试验;研究Ti6Al4V合金高温下的应力松弛行为以及影响因素。利用应力松弛的试验数据推导出高温短时蠕变应变速率与应力的关系,对蠕变应变速率-应力曲线进行拟合,得到Ti6Al4V合金的高温短时蠕变本构方程。将高温短时蠕变本构关系代入有限元软件ABAQUS中对Ti6Al4V合金的应力松弛行为进行模拟。结果表明:Ti6Al4V合金的应力松弛可以分为两个阶段:第一个阶段应力松弛速率很快,剩余应力急剧降低,该过程时间为应力松弛的前250 s;第二个阶段应力松弛较为缓慢,经过2000 s后剩余应力趋向于某一极限值,即应力松弛极限。温度对Ti6Al4V合金应力松弛的影响显著,应力松弛随温度的升高而加快,且温度越高,应力松弛极限越小。初始应力和预应变越大,应力松弛极限越大,但是两者对应力松弛行为的影响不大。模拟结果与试验测得的应力松弛曲线具有很高的吻合度,验证了高温短时蠕变本构关系的可靠性。

The stress relaxation tests of Ti6A14 V alloy were conducted at different temperatures（650,700 and 750℃）,initial stresses（100 and 150 MPa）,pre-strains（3.97%and 15.87%）.The stress relaxation behavior of Ti6A14 V alloy and influence of different factors at high temperature were discussed.Based on the experimental data of stress relaxation,the relationship between short-term creep strain rate and stress was deduced.Then,the short-term creep constitutive equation of Ti6A14 V alloy at high temperature was obtained by fitting the creep strain rate-stress curves.The short-term creep constitutive relation at high temperature was used to simulate the stress relaxation behavior of Ti6Al4 V alloy by integrating the relation into finite element software ABAQUS.The results show that the stress relaxation of Ti6Al4 V alloy can be divided into two stages：At the first stage,the stress relaxation rate is very fast and the residual stress reduces sharply,which lasts 250 s,While at the second stage,the stress relaxation rate is relatively slow and the residual stress tends to the limit after 2000 s.Temperature has significant influence on the stress relaxation of Ti6A14 V alloy.The rise of temperature can accelerate the stress relaxation rate,and the higher the temperature is,the smaller the stress relaxation limit is.Stress relaxation limit increases with the increase of initial stress and pre-strain which have small effect on the stress relaxation behavior.The simulated results and the experimental stress relaxation curves are with a high degree of similarity,which validates the dependability of the short-term creep constitutive relation at high temperature.