时效处理对GH4169合金显微组织及高温拉伸变形行为的影响

研究了在900 ℃超温服役的试验条件下,时效时间对GH4169合金的显微组织形貌、显微硬度和高温拉伸性能的影响。结果表明:随着时效时间的延长,δ相先由晶界呈短棒状析出,然后以长针状覆盖整个晶粒。时效初期晶粒有长大现象,随着δ相沿晶界的不断析出,晶粒长大现象消失。900 ℃时效处理使得GH4169合金强化相发生溶解与转化,致使合金显微硬度从44 HRC急剧降至13.6 HRC,但后续保温时间的延长对显微硬度影响较小。δ相的析出对合金的高温力学性能有显著影响,适量的析出提高了合金的抗拉强度和高温塑性,大量析出则导致合金抗拉强度变低,高温塑性变差;不同时效处理后的合金高温拉伸均为典型的弹性-均匀塑性变形,变形断裂机制皆为微孔聚集型断裂。

Effect of aging treatment on microstructure and high temperature tensile deformation behavior of GH4169 alloy

Effect of aging time on microstructure, hardness and high temperature tensile properties of GH4169 alloy under the tested conditions of over-temperature service at 900 ℃ were studied. The results show that with the extension of aging time, the δ phase is precipitated from the grain boundary with a short rod shape, and then precipitated the whole grain with long needles; the grain is grown at the initial stage of aging, and with the δ phase gradual precipitating along the grain boundary, the phenomenon of grain growth is disappeared. The strengthening phase of the alloy is dissolved and transformed when the GH4169 alloy aged at 900 ℃, which results in the microhardness of the alloy dropping sharply from 44.0 HRC to 13.6 HRC, but the microhardness is changed a little with the increase of holding time. The precipitation of δ phase has a significant effect on the high temperature mechanical properties of the alloy. The proper amount of precipitation can increase the tensile strength and high temperature plasticity of the alloy. A large amount of precipitation results in a decrease of tensile strength and a deterioration on the high-temperature plasticity. The high temperature tensile of the alloy after different aging treatments is a typical elastic-uniform plastic deformation, and the deformation fracture mechanism is a microporous aggregate fracture.