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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。
Three-point bending specimens were selected. The fracture toughness of GH690 alloy was evaluated from room temperature to 623K by J-integral method. The fracture behavior of the alloy at different temperatures was investigated. The results show that the fracture toughness of GH690 alloy decreases with the increase of temperature. Due to the low stacking fault energy at room temperature, the deformation of the alloy can be coordinated by the twins. However, the deformation twin induces crack propagation and elongation, which prolongs the crack growth path and makes the alloy exhibit higher fracture toughness. With the increase of temperature, The stacking fault can increase, the probability of deformation twins decreases, and the crack growth direction decreases, leading to the decrease of the fracture toughness of the alloy.