高温时效时间对定向凝固DZ951镍基高温合金组织和持久性能的影响

采用光学显微镜和扫描电子显微镜研究了高温时效时间对DZ951合金组织及其持久性能的影响。结果表明,合金在1130℃高温时效时,碳化物由铸态时的骨架状变成块状,呈不连续状分布在晶界。随着保温时间的延长,γ′立方度降低,尺寸增加。保温6h时,γ′粗化形筏。合金在1130℃高温时效时,由于γ′部分固溶,并在随后的冷却过程中析出细小球形γ′相,随着保温时间的增加,细小γ′相的体积分数增多。DZ951合金在1100℃,60MPa的持久寿命随保温时间增加而降低,延伸率增加。γ′粗化形筏对合金持久寿命是不利的。

Influence of High-Temperature Aging Time on Microstructure and Stress Rupture Property of Directionally Solidified DZ951 Ni-Based Superalloys

Influence of high-temperature aging time on microstructure and stress rupture property of DZ951 superalloys was investigated by optical microscopy (OM) and scanning electronic microscopy (SEM). The results reveal that carbide changes from skeleton-like of as-cast alloy to block-like and discontinuously distributes in grain boundary when the alloy is aged at 1130 °C. γ' cubicity decreases and the size of γ' phase increases with the elongation of holding time at 1130 °C. γ' coarsens and rafts when the holding time is 6 h. For solid solution of some g￠, fine and sphericalγ' phase precipitates during the following cooling process after 1130 °C aging treatment. The volume fraction of fineγ' phase increases with prolonging the holding time. The stress rupture life of DZ951 alloy at 1100 °C/60 MPa reduces and the elongation increases with the prolongation of holding time. Coarsening and rafting of γ' is deleterious to the stress rupture life for alloys.