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研究了具有初始等轴组织的TC4-DT钛合金在变形和未变形的状态下在β单相区等温加热时的晶粒长大动力学。变形在两相区进行,变形程度为60%,变形后空冷。加热温度分别选取相变点以上10、20、30℃,保温时分别为2、5、10、30、60、120 min。利用金相分析软件对晶粒尺寸进行了定量测定并分析获得了两种条件下的晶粒生长的时间指数和激活能。未变形试样的晶粒生长的时间指数和激活的变化范围分别是0.34~0.35和86.8~130 kJ·mol-1,在变形条件下变为0.36~0.39和76.6~110 kJ·mol-1。研究结果表明在相同的加热条件下,变形试样具有较高的晶粒生长指数和较低的生长激活能。这是因为晶粒生长时间指数随温度的变化和生长激活能随时间的变化与固溶原子的扩散和晶界的迁移的交互作用有关,而变形可以促进原子的扩散和晶界的迁移。另外还研究了在不同的加热温度、时间以及变形条件下晶粒尺寸的均匀度的变化情况,这种变化是β相的形核速率和生长速率在上述因素的影响下共同作用的结果。
The grain growth kinetics of TC4-DT titanium alloy with initial equiaxed microstructure under isothermal heating in β-phase region was investigated in the deformed and undeformed state. Deformation in the two-phase zone, the degree of deformation of 60%, air-cooled after deformation. Heating temperature were selected above the phase transition point 10,20,30 ℃, respectively, when the heat preservation 2,5,10,30,60,120 min. The grain size was quantitatively determined by metallographic analysis software and the time index and activation energy of grain growth under the two conditions were obtained. The time index and the activation range of the grain growth of the undeformed samples are 0.34-0.35 and 86.8-130 kJ · mol-1, respectively, and are 0.36-0.39 and 76.6-110 kJ · mol-1 under the deformation conditions. The results show that under the same heating conditions, the deformed samples have higher grain growth index and lower growth activation energy. This is because the change of the grain growth time index with temperature and the change of the growth activation energy over time are related to the interaction between the solution diffusion and the grain boundary migration, and the deformation can promote the atom diffusion and the grain boundary migration. In addition, the variation of the uniformity of the grain size under different heating temperature, time and deformation conditions was also studied. The change is the result of the interaction between the β-phase nucleation rate and the growth rate under the influence of the above factors.