不同温度下GH690合金断裂韧性及断裂行为

Fracture Toughness and Fracture Behavior of GH690 Alloy at Different Temperatures

选取三点弯曲试样、采用J积分方法评价了GH690合金从室温到623K的断裂韧性,考察了不同温度下合金的断裂行为。结果表明,GH690合金的断裂韧性随着温度的升高而降低。由于室温层错能较低,合金变形可以通过孪生协调进行,而形变孪晶诱导裂纹扩展转向,延长了裂纹的扩展路径,使合金表现为较高的断裂韧性;随着温度的升高,合金的层错能增加,形变孪晶生成的机率降低,裂纹扩展转向减少,导致合金的断裂韧性随之降低。

The fracture toughness and fracture behavior of GH690 alloy were investigated by means of three-point bending tests and the J-integral method in the range of the room temperature to 623 K.The results show that the fracture toughness of the alloy decreases with the increasing of testing temperature. The stacking fault energy of GH690 alloy is low at room temperature and the alloy was deformed by twinning.Deformation twins perpendicular to the main crack could lead to the deflexion of the crack, which is beneficial to the enhancement of the fracture toughness.However,with the testing temperature elevated,the stacking fault energy increases and the number of the deformation twins decreases,allowing an easier propagation of the crack and is responsible for the decrease of the fracture toughness of GH690 alloy.