BT25钛合金在两相区变形过程中的显微组织定量分析

Quantitative metallography analysis of microstructure of BT25 titanium alloy deformed in two-phase field

对具有片层α相的BT25合金圆饼在两相区进行4种变形程度的等温锻造,用定量金相分析方法研究变形量对显微组织特征参数(α相体积分数、α片层厚度和α相球化率)的影响规律。结果表明:随着变形量增加,α片层不断弯曲破碎,导致α片层长宽比减小而球化率增大,当变形量达到80%时球化率为85.23%,改善了合金组织的均匀性;在变形过程中片层α两端的物质向中间扩散,导致片层厚度增加,变形量从0%增至80%,α片层厚度增加了1.6μm;α相的体积分数由于等温锻造温度不变而基本维持在60%左右,大变形时有所降低。

The isothermal compression of BT25 titanium alloy with initial lamellar was carried out with four deformation degrees and the effect of deformation degree on microstructure parameters （volume fraction, thickness and globularization ratio ofαphase） was investigated based on quantitative metallography. The results show that the process ofαlamellar pinch-off/fragmentation takes place with increasing the deformation degree, which results in the decrease of the Feret ratio ofαlamellar and the increase of globularization ratio. It reaches 85.23%when the deformation degree is 80%. The microstructure homogeneity of the alloy is improved. Mass diffusion from both ends of αlamellar to center happens during the deformation process, making the thickness of α phase increase （about 1.6 μm with increasing deformation degree from 0% to 80%）. The volume fraction of α phase （about 60%） remains unchanged because of a stable deformation temperature. However, it decreases slightly in the case of high forging strains.