在真空定向凝固炉中采用螺旋选晶法制备了一种镍基单晶高温合金, 对其进行标准热处理后在1 070 ℃时效200, 400, 600, 800 h, 然后采用扫描电镜和透射电镜对其组织稳定性进行了研究。结果表明: 合金经热处理后, 获得规则立方状的γ′相组织; 在1 070 ℃的长期时效过程中, 随着时效时间的延长, γ′相合并长大, γ基体通道变宽, 时效800 h后, 合金基本形成完善的筏形组织; 时效200 h后无TCP相析出, 时效400 h后枝晶干有少量针状TCP相析出, 随着时效时间延长, 析出的TCP相增多, 并由枝晶干向枝晶间延伸; TCP相主要由铼、钨、钼和钴等元素组成, 为σ相, 与基体存在的取向关系为[001]σ//[112]γ, (11-0)σ//(22-0)γ。

A Nickel based single crystal superalloy was prepared by screw selecting method in vacuum directionally solidified furnace. The microstructure and its stability were investigated by SEM and TEM after the alloy experienced standard heat treatment and then was aged for 200, 400, 600, 800 h at 1 070 ℃. The results show that the regular and cube γ′ phases were obtained after fully heat treatment of the alloy. The γ′ coarsening and the γ matrix channel broadening with time were observed in the long term aging at 1 070 ℃. The full γ′ rafting formed after long term aging for 800 h. No TCP phase precipited after long term aging for 200 h. Needle shaped TCP phase precipitated on dendritic crystals in the alloy after long term aging for 400 h. With aging time extension, the precipitated TCP phase increased and grew up from dendritic crystal region to interdendritic region. The TCP phase was mainly composed of Re, W, Mo and Co and so on. TCP phase was identified as σ phase, which precipitated and grew along fixed direction, [001] σ//[112]γ , (11-0)σ//(22-0)γ。