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针对高压热处理能改善(α+β)钛合金组织的问题,对TC6钛合金进行5 GPa压力,1000℃保温20 min的高压热处理,利用差示扫描量热仪(DSC)测试了高压热处理前后TC6钛合金在不同升温速率下的α→β相变温度和转变时间,根据Deloy方程和Ozawa方程分别计算其相变激活能和Avrami指数,并利用光学显微镜(OM)和透射电镜(TEM)对高压热处理前后TC6钛合金的组织进行观察,探讨了高压热处理对TC6钛合金中α→β相变动力学的影响。结果表明:5 GPa压力热处理能降低TC6钛合金的α→β相变温度,缩短相变时间,增大相变激活能。当合金以20℃·min~(-1)升温时,5 GPa压力热处理能使α→β相变起始温度和相变结束温度较5 GPa压力处理前分别降低了4.88和8.71℃,相变时间也减少了0.2 min。当相变体积分数为50%时,5 GPa压力处理后合金的α→β相变激活能较5 GPa压力处理前增大了155.29k J·mol~(-1),但高压热处理对α→β相变机制影响不大。其原因主要是高压热处理能增大TC6钛合金组织中的晶界密度和位错密度。
In order to improve the microstructure of (α + β) titanium alloy, the TC6 titanium alloy was subjected to high pressure heat treatment at 5 GPa and 1000 ℃ for 20 min. The effects of high pressure heat treatment before and after TC6 The phase transformation temperature and transformation time of titanium alloy at different heating rates were calculated according to Deloy equation and Ozawa equation respectively. The activation energy and Avrami index of titanium alloy were calculated by optical microscope (OM) and transmission electron microscope (TEM) The microstructure of TC6 titanium alloy before and after heat treatment was observed, and the effect of high pressure heat treatment on α → β phase transformation kinetics in TC6 titanium alloy was discussed. The results show that 5 GPa heat treatment can decrease the α → β transformation temperature, shorten the phase transformation time and increase the phase transformation activation energy. When the alloy is heated at 20 ℃ · min ~ (-1), the 5 GPa pressure heat treatment can reduce the onset temperature of α → β phase transformation and the end temperature of phase transformation by 4.88 and 8.71 ℃, respectively, compared with that before 5 GPa pressure treatment. The time is also reduced by 0.2 min. When the volume fraction of phase transformation is 50%, the activation energy of α → β phase transformation increases by 155.29k J · mol -1 after 5 GPa pressure treatment compared with that before 5 GPa pressure treatment. However, β phase transition mechanism has little effect. The reason is that high pressure heat treatment can increase the grain boundary density and dislocation density in the TC6 titanium alloy.