多道次温轧TC4钛合金超塑性变形行为与断裂机制

Superplastic Deformation Behavior and Fracture Mechanism of Multi-pass Warm Rolled TC4 Titanium Alloy

在温度为700~870℃和应变速率为0.001~0.01s^(-1)条件下对多道次温轧TC4钛合金板材进行超塑性拉伸试验,研究该合金的低温超塑性变形行为与断裂机制。发现最佳超塑性变形条件为800℃,0.001s^(-1),试验获得的最大伸长率为1 550%。在温度为700℃、应变速率为0.001s^(-1)和0.01s^(-1)时,伸长率分别为576%和356%。多道次温轧形成的细小晶粒、破碎弥散分布的β相以及变形过程的动态再结晶均有利于提高合金的超塑性。合金的应变速率敏感系数m值随温度升高而增加;在800℃和870℃超塑性变形时的激活能分别为226.8和220.2kJ/mol,在700℃时激活能增大到377.5kJ/mol。合金超塑性断裂是由内部孔洞长大连接和外部缩颈共同作用导致的。

The low temperature superplastic deformation behavior of TC4alloy was investigated by the tensile tests for multi-pass warm rolled TC4alloy at 700-870℃and 0.001-0.01s^（-1）.A maximum elongation of 1 550%can be obtained at 800℃and 0.001s^（-1）.At 700℃,the elongation of the Ti alloy at0.001s^（-1 ）and 0.01s^（-1 ）reach 576%and 356%,respectively.The enhanced superplastic ductility can be attributed to the refined microstructure with fragmented and uniformly distributed fineβgrains as well as dynamic recrystallization.The coefficient of strain rate sensitivity is increased with the temperature increase.The activation energy of the alloy at 800℃and 870℃reach 226.8kJ/mol and 220.2kJ/mol,however,it is increased to 377.5kJ/mol at 700℃.The fracture of alloy is controlled by the interaction of internal cavity growth and external necking.