TC21新型钛合金的超塑性拉伸行为及组织演化

The Superplastic Tensile Deformation Behavior and Structure Evolution of New Type Titanium Alloy-TC21

研究了新型高强高韧高损伤容限TC21钛合金的超塑性拉伸变形行为及组织演化规律。结果表明,TC21合金具有良好的超塑性和较宽的超塑性温度-应变速率范围(720℃～960℃,5.5×10^(-5)／s～1.1×10^(-2)／s)。在最佳超塑性条件下(900℃,3.3×10^(-4)／s),平均延伸率达到980％,最高延伸率达到1309％,平均流动应力仅为19.5 MPa。在超塑性拉伸过程中,试样变形区将发生明显的动态再结晶,使原始条状初生α相破断、细化和等轴化,促进超塑性的提高。随着变形温度提高、变形量增大和变形时间加长,将发生聚集再结晶,使再结晶α相合并长大成不规则的大片状,引起显微组织明显粗化,断口表面起伏增加。在最佳超塑性条件下,断口中形成了大而深的空洞,晶界滑动和晶间断裂特征明显。

The superplastic tensile deformation behavior and the structure evolution law of high strength, high toughness and high damage-tolerant titanium alloy-TC21 have been investigated. The experimental results show that TC21 titanium alloy has good superplasticity and wider temperature-strain rate range （720℃-960℃, 5.5 × 10^-5/s-1.1×10^-2/s）. On the optimal superplastic condition （900℃, 3.3 × 10^-4/s）, the average elongation is 980%, the maximum elongation is 1309%, however, the average flow stress is only 19.5 MPa. During the superplastic tensile deformation, the dynamic recrystallization occurs in deformation zone of specimen and the original strip primary a phase is cracked, refined and equiaxed, so that the superplasticity can be improved. With increasing of temperature and deformation amount and deformation time, collective recrystallization will occur, recrystallization a phase will merge and grow up into irregular big strip, causing obvious coarsing of microstructure and increasing of the undulation of fracture surface. The deep and large cavities are formed on fracture surface and grain boundary sliding and intergranular fracture characteristic is obvious on the optimal superplastic deformation condition.