铸态TB6钛合金热变形过程中应力诱发马氏体相变

Stress induced martensitic transformation of as-cast TB6 titanium alloy during hot process

摘要:

对铸态TB6钛合金进行了恒应变速率热模拟压缩试验（变形温度为800~1150 ℃、应变速率为0.001~10 s-1），研究了合金微观组织演变和应力诱导马氏体（SIM）相变。结果表明，该合金在热变形过程中出现了具有枝晶形态的正交结构SIM。SIM在β晶内和晶界形核。应变速率和变形温度控制合金成分均匀性和内应力，是SIM析出量的主要影响因素。不同应变速率的SIM析出量与变形温度范围有关。SIM析出量较高变形条件为：在800~900 ℃时应变速率为0.1 s-1，900~1000 ℃时应变速率为0.01和1 s-1，在1000 ℃以上时应变速率为1 s-1。在变形温度925 ℃、应变速率1 s-1时SIM析出量达最大化为50%。

关键词:铸态TB6钛合金; 马氏体; 热变形

Abstract:

Hot compression tests of as-cast TB6 titanium alloy were performed at the temperature of 800-1150°C and the strain rate range of 0.001-10s_^?1 to examine microstructure evolution associated with stress induced martensite (SIM). The results reveal the occurrence of the SIM with the dendritic morphology in present alloy during hot compression process. The orthorhombic structure of SIM was confirmed for the alloy. It was found that the SIM nucleates both in the β grain interior and at grain boundary. TheSalloy composition uniformity and internal stress are strongly dominated by strain rate and deformation temperature, which is responsible for the amounts of SIM. The content of SIM at different strain rate is related to the temperature ranges. More contents of SIM appear at the strain rate of 0.1s_^-1 for the temperature of 800℃~900℃, at 0.01s_^-1 and 1s_^-1 for the temperature of 900℃~1000℃, at the strain rate of 1s_^-1 for the temperature of above 1000℃. 50% martensite can be obtained at an optimal combination of the temperature of 925℃ and the strain rate range of 1s_^-1.

Key words:as-cast;TB6 titanium;alloy, martensite, hot;process