长期时效过程中GH4586合金的微观组织演变机理

Mechanism of microstructure evolution of GH4586 superalloy during long-term aging process

系统研究了航空涡轮盘GH4586A和GH4586B合金在700～800℃长期时效时,合金微观组织的演变过程.重点研究了时效过程中沉淀强化相与奥氏体基体的稳定性,尤其是拓扑密排相(TCP相)析出行为及其与时效温度和时效时间的关系.研究表明,长期时效过程中GH4586B合金未见TCP相析出,但γ'相随时效时间的延长快速粗化,导致合金室温与高温强度显著衰减.GH4586A合金的γ'相长大缓慢,从而保持了稳定的抗拉强度,但在750℃、2 000 h以上时效时出现了μ相析出在晶界与晶内M6C二次碳化物表面形核并以半共格形式向奥氏体基体内生长,致使合金的塑性有所下降.

Microstructure evolution during long - term aging from 700 ℃ to 800℃ of two experimental alloys GH4586A and GH4586B was studied. Morphological stability of austenite grain boundary and γ phase, and precipitation behavior of TCP phases were evaluated. The results show that there is no TCP phase presented during aging process, while γ phase ripen rapidly and lead to decrease of tensile strength at both room and elevated temperatures. The size and morphology of γ phase in GH4586A maintain stable, which ensures GH4586A with relatively high tensile strength after a long term exposure. The phase was observed in GH4586A when aging time was longer than 2000 hours at higher than 750 ℃, which induces a deterioration of ductile. TEM observation shows that the μ phase mainly nuclear on the MtC secondary carbides.