TA32钛合金板材的超塑性能研究

Research on Superplastic Behavior of TA32 Titanium Alloy Plate

摘要:

研究了真空环境中TA32钛合金板材在温度950℃、应变速率5. 32×10~(-4)～2. 08×10~(-2)s~(-1)条件下的超塑性变形行为。结果表明,在不同应变速率条件下,合金的流变应力曲线特征和显微组织演变显著不同。在应变速率较低(5. 32×10~(-4)～3. 33×10~(-3)s~(-1))条件下,拉伸真应力-真应变曲线呈传统超塑变形的稳态流动特征,变形后的合金中初生α相晶粒尺寸较大;在高应变速率(8. 31×10~(-3)s~(-1)～2. 08×10~(-2)s~(-1))条件下,拉伸真应力-真应变曲线中流变应力增大到峰值后快速单调递减直至试样断裂,合金变形过程中初生α相发生动态再结晶,晶粒尺寸较低应变速率条件下显著细化。950℃时,TA32钛合金板材均具有超塑性变形能力,超塑性延伸率在145%～519%之间;当应变速率为5. 32×10~(-4)s~(-1)时,具有最佳的超塑性,拉伸延伸率可达519%。断裂区形貌分析发现,TA32钛合金板材的超塑性断裂模式为空洞聚集-连接-长大型断裂。

Abstract:

The superplastic behavior of TA32 titanium alloy plate at 950 ℃ in vacuum environment was studied at a range of strain rate from 5. 32 × 10~(-4) s~(-1) to 2. 08 × 10~(-2) s~(-1). The results show that,the characteristics of true stressstrain curves and microstructure evolution of TA32 titanium alloy plate are significantly different under different strain rates. Under the deformation condition of low strain rates( 5. 32 × 10~(-4)～ 3. 33 × 10~(-3) s~(-1)),the true stress-strain curves exhibit typical feature of traditional steady-state superplasticity,and the grain sizes of primary α phases are increased after deformation. While under the deformation condition of high strain rates( 8. 31 × 10~(-3)～ 2. 08 × 10~(-2) s~(-1)),the flow stress rapidly monotonically decreases until fracturing after reaching the peak point,and the grain sizes of primary α phases are significantly finer than those at low strain rates as result of dynamic recrystallization refinement.TA32 titanium alloy plate shows excellent superplastic deformation ability at 950 ℃ with an elongation to fracture from 145% to 519%. At the strain rate of 5. 32 × 10~(-4) s~(-1),it has the biggest elongation of 519%. It is found that the superplastic fracture mode of TA32 titanium alloy plate is the aggregation-linkage-growth of vacancies.