工艺参数对粗晶Ti2AlNb合金超塑性行为的影响

研究了粗晶状态(200～800μm)的Ti-22Al-25Nb合金在1213～1263 K温度范围内和3.3×10-4～3.3×10-2s-1初始应变速率范围内的超塑性性能与变形工艺参数之间的关系,探讨了温度和应变速率变化对合金延伸率的影响规律,并根据合金在变形过程中的流变应力变化对合金的本构方程进行了求解。结果表明,在上述条件下粗晶状态的合金也表现出一定的超塑性,较佳变形温度为T=1238 K,较佳初始应变速率为3.3×10-4s-1,延伸率达到370%,合金的延伸率随应变速率的降低而增大。通过对合金变形过程相关数据进行计算,合金的热变形激活能为759.918 kJ/mol,合金的变形机制主要表现为动态再结晶和新相长大。

Effects of Process Parameters on the Superplastic Behavior

Superplastic behaviors of coarse-grained Ti-22Al-25Nb alloy were investigated at temperatures ranging of 1213~1263 K and initial strain rate raging of 3.3×10-4~3.3×10-2s-1. The constitutive equation has been established according to the flow stress of the alloy during the deformation process. The results show that the alloy exhibits a certain degree of superplasticity under above conditions. The maximum elongation exceeds 370% at 1238 K and 3.3×10-4s-1. The elongation of the alloy increases with decreasing of strain rate. The average apparent activation energy of the alloy was calculated to be 759.918 kJ/mol. The deformation mechanism of the alloy mainly is dynamic recrystallization and the new phase growth up