声速法研究时效温度对Ti27Nb8Zr合金弹性性能影响

Research on effect of aging temperature on elastic property of Ti27Nb8Zr by using acoustic velocity method

将Ti27Nb8Zr合金进行固溶时效处理,应用超声水浸聚焦法并结合纵波掠入射方法测量超声波在各个时效样品中的传播速度,基于声波在各向同性、均匀固体介质中的传播规律,推算时效样品的弹性性能指标.结果表明:随时效温度的升高,声速和弹性性能指标逐渐降低,泊松比增大.分析认为:随着时效时间的延长,马氏体逐步分解成形态与含量均不同的相,该过程导致合金弹性性能指标的变化.对应350、400℃时效组织均为β+ω相,故二者弹性性能指标的变化较小;450℃的时效组织则由β、ω相及少量的α相组成,ω相的减少以及α和β相的逐渐增多导致弹性性能指标降低;500℃时,时效组织完全由α相和β相组成,ω相的消失使得弹性性能指标进一步降低.

Ti27Nb8Zr was subjected to solid solution treatment and aging treatment.Using ultrasonic water immersion focusing method combining with longitudinal grazing incidence method,ultrasonic wave velocities in aging specimens were measured.Based on the rule of acoustic wave propagating in isotropic homogeneous solid medium,the elastic indices of aging specimens were deduced.The results show that acoustic velocity and elastic indices decrease and Poission raito increases with the increase of aging temperature.It is considered that the decomposed phases with various morphologies and contents from martensite during aging have influence on the elastic indices.The aging structure of 350 ℃ and 400 ℃ is β＋ω phase,therefore,elastic indices change slightly;the microstructure of 450 ℃ consists of β phase,ω phase and a small quantity of α phase,and the decrease of ω phase and the increase of α,β phase cause the decline of elastic indices.When aging temperature elevates to 500 ℃,aging structure makes up of α phase and β phase,and elastic indices decrease further for the disappearance of ω phase.