FGH97粉末高温合金的断裂特征

Fracture Features of FGH97 Powders Superalloy

对FGH97粉末高温合金低周疲劳、高周疲劳和持久断裂特征进行了研究。结果表明:低周疲劳断裂在小应变条件下的裂纹源为单裂纹源,疲劳裂纹稳定扩展第一阶段为类解理小平面特征;在大应变条件下,裂纹源转变为多源,疲劳扩展第一阶段即可见疲劳条带特征;高周疲劳裂纹稳定扩展第一阶段有较大区域的类解理断裂小平面,疲劳扩展第二阶段为疲劳条带特征;持久试验温度为500℃时,断口为穿晶特征,表现为类解理形貌;在500℃以上时,其断裂机制为晶内发生单取向和双取向滑移,随蠕变进行位错在晶界处塞积,进而引起应力集中,致使裂纹在晶界处萌生并扩展。

The fracture features of FGH97 powders superalloy were studied under the conditions of low-cycle fatigue, high-cycle fatigue and stress rupture. The results show that the low-cycle fatigue fracture surfaces had only one source at low strain, and the characteristics at the first stage of fatigue crack expanding was similar cleavage planes. However, at high strain, the low-cycle fatigue fracture surfaces had multi-sources, and the characteristics at the first stage of fatigue crack expanding was fatigue striations. The large range of similar cleavage planes existed at the first stage of fatigue crack expanding on the high-cycle fatigue fracture surfaces, and the characteristics at the second stage of fatigue crack expanding was fatigue striations. The characteristics of stress ruptured zone was transgranular similar cleavage at 500 ℃, and above 500 ℃, the characteristics was one and two way siipping of dislocations activated in the alloy as deformation goes on, some of dislocations congregated at the grains boundary regions to bring the stress concentration which promoted the initiation and propagation of the microcracks, which was thought to be the fracture mechanism of FGH97 powders superalloy during stress rupture.