热处理对第二代镍基单晶合金DD11显微组织及持久性能的影响

Effects of heat treatment on microstrucutures and stress rupture properties of a second generation Ni-based single crystal DD11

采用光学显微镜和扫描电镜对铸态、固溶态和时效态的第二代镍基单晶合金DD11的显微组织进行定量表征,并测试了不同一级时效处理后的合金1 100℃/140MPa和980℃/250MPa条件下的持久性能。结果表明:合金经过1 320℃/6h固溶处理后,(γ+γ′)共晶相全部溶解,凝固偏析显著降低,合金组织均匀。一级时效温度低于1 160℃时,γ′相为方形,一级时效温度高于1 180℃时,γ′相为球形,γ通道显著变宽,并在通道内析出细小的γ′相。随一级时效温度提高,合金的持久寿命先增大后降低。持久性能与γ′相尺寸、体积分数及形态密切相关。

The quantitative investigation of as-cast, as solution and ageing heat-treated microstructures of a second generation Ni-based single crystal DDll was carried out through OM and SEM. The stress rupture properties of the alloys which had been first ageing treated under 1100 ℃/140 MPa and 980 ℃/250 MPa respectively were also tested. The results indicate that （γ＋γ′） eutectic is almost＇dissolved when DDll is under solution treatment of 1320 ℃/6 h. And the degree of solidification segregation significantly decreases, and the alloy exhibits uniform microstructure. When the first ageing treatment temperature is lower than 1160 ℃, the shape of γ′ phase is cubic. But the shape transforms to sphericity when the aging temperature is higher than 1 180 ℃, the width of 7 phase channel greatly increases, and fine γ′ phase precipitates in the γ phase channel. With the increase of the first ageing treatment temperature, the stress rupture live of the alloy increases first and then decreases. The stress rupture properties are closely related to the size, the volume fraction and the morphology of γ′ phase.