TC18钛合金的超塑性行为与变形机制

通过高温拉伸实验研究TC18钛合金在温度为720~950℃,初始应变速率为6.7×10~(-5)~3.3×10~(-1)s~(-1)时的超塑性拉伸行为和变形机制。结果表明:TC18钛合金在最佳超塑性变形条件下(890℃,3.3×10~(-4)s~(-1)),最大伸长率为470%,峰值应力为17.93MPa,晶粒大小均匀。在相变点Tβ(872℃)以下拉伸,伸长率先升高后下降,在温度为830℃,初始应变速率为3.3×10~(-4)s~(-1)时取得极大值373%,峰值应力为31.45MPa。TC18钛合金在两相区的超塑性变形机制为晶粒转动与晶界滑移,变形协调机制为晶内位错滑移与攀移;在单相区的超塑性变形机制为晶内位错运动,变形协调机制为动态回复和动态再结晶。

Superplastic Behavior and Deformation Mechanism of TC18 Titanium Alloy

Superplastic tensile behavior and deformation mechanism of TC18 titanium alloy were investigated by high temperature tensile test at 720-950 ℃ with initial strain rates of 6.7 × 10-5 s-1-3.3 ×10-1 s-1.The results show that under the optimal superplastic deformation condition (890 ℃ and 3.3 ×10-4 s 1),the maximum elongation is 470 ％,the peak stress is 17.93MPa and with uniform grain size.Below the phase transus Tβ,the elongation firstly increases and then decreases.A maximum elongation of 373 ％ is obtained at 830 ℃ and with initial strain rate of 3.3 × 10-4s-1 and the peak stress is 31.45MPa.The superplastic deformation mechanism of the TC18 titanium alloy in two-phase region is mainly grain rotation and boundary sliding,and the deformation coordination mechanism is dislocation slipping and climbing;the superplastic deformation mechanism in single phase region is intragranular dislocation motion and the deformation coordination mechanism is dynamic recovery and dynamic recrystallization.