长期时效温度对一种单晶高温合金组织和拉伸性能的影响

在定向凝固炉中采用螺旋选晶法制备了一种单晶高温合金试棒，标准热处理后分别在980 ℃，1 070 ℃，1 100 ℃和1 140 ℃长期时效处理500 h，研究了不同温度长期时效后合金的显微组织和1 100 ℃的拉伸性能.结果表明合金在不同温度长期时效后，γ′相发生粗化或筏排化.随着时效温度增加，γ′相粗化或筏排化程度增加，γ′相体积分数减少，γ相基体通道变宽.在980 ℃长期时效500 h后，无TCP相析出；1 070 ℃，1 100 ℃，1 140 ℃长期时效500 h后，有针状TCP相析出.随着长期时效温度增加，TCP相含量增加.随着时效温度升高，合金拉伸强度降低，拉伸延伸率先增加后在1 140 ℃时效时又降低.长期时效后γ′相粗化或筏排化、γ′相含量减少和TCP相析出是合金拉伸强度降低的主要原因. 

Effect of long-term aging temperature on the microstructure and tensile properties of a single crystal superalloy

A nickel-based single crystal superalloy was casted using the directional solidification furnace. The long term aging of the alloy was performed at 980 ℃, 1 070 ℃, 1 100 ℃ and 1 140 ℃ for 500 h, respectively. The microstructure and tensile properties at 1 100 ℃ of the alloy after long term aging at different temperature were investigated. The results show that the γ′ phase directional coarsening or rafting and the γ matrix channel widen can be observed in the alloy after long term aging. The coarsening extent of γ′ phases increased and the volume fraction of γ′ phase decreased and space of γ matrix channel obviously increased with rise of aging temperature. No TCP phase was found in the alloy after aging at 980 ℃ for 500 h. The needle shaped TCP phase precipitated after long term aging at 1 070 ℃, 1 100 ℃ and 1 140 ℃ for 500 h. The volume fraction of TCP phase increased with rise of aging temperature. With rise of aging temperature, the yield strength and ultimate tensile strength all decreased with rise of aging temperature, while the elongation increased at first and decreased afterward when aging at 1 140 ℃.