三重热处理对TC21合金超塑性变形后组织的影响

Effects of Triple Heat Treatment on Superplastic Tensile Microstructure of TC21 Alloy

对TC21钛合金进行超塑性拉伸和三重热处理试验,研究了三重热处理对TC21钛合金超塑性拉伸后组织的影响。结果表明,TC21钛合金在超塑性变形过程中发生明显的动态再结晶,α相含量随着变形温度的升高而减少,并发生α→β转变;TC21钛合金超塑性变形后经β相区固溶第一重热处理获得单相β组织,随后在(α+β)相区进行一次高温时效和一次低温时效,使细小针状α相在β基体中析出,得到网篮组织。针状α相含量随着变形温度和第二重温度的升高而增多,α晶粒长大并相互交织,网篮组织编织明显。

After superplastic tensile deformation and triple heat treatment, the effects of triple heat treatment on superplastic tensile microstructure of TC21 titanium alloy were investigated. The results show that dynamic recrystallization occurred obviously in the process of TC21 titanium alloy superplastic deformation. The α phase content became more decrease with increase of deformation temperature and α？β phase transition start to happen. After superplastic deformation and β solid solution heat treatment for the first time, TC21 titanium alloy obtain single-phase β organizations. Through a high temperature aging and a low temperature aging in the （α β） phase region, fine acicular α phase precipitates out on β matrix, and TC21 alloy obtain baskets organizations. Acicular α phase content increases with the increase of deformation temperature and the second heat treatment temperature. With the increase of deformation temperature and the second temperature, acicular α phase content increases, and α grain grew up and intertwined which basketweave microstructure significantly.