Co-9Al-(9－x)W-xMo-2Ta-0.02B (x=4,9)合金的显微组织与高低温拉伸性能

Microstructure and Mechanical Properties of Co-9Al-xMo-(9–x)W-2Ta-0.02B(x=4, 9) Alloy at Room and High Temperatures

摘要:

以Co基高温合金Co-9Al-9W-2Ta-0.02B成分为基础，分别添加了4at%和9at%的Mo元素替代W (使W+Mo含量为9at%)，用电弧熔炼法制备了Co-9Al-xMo-(9－x)W-2Ta-0.02B合金 (x = 4, 9)，分别称为4Mo和9Mo合金，研究了Mo含量及时效温度对合金相组成、显微组织形貌和高低温拉伸性能的影响。结果表明：铸态合金由Co的固溶体γ相基体和金属间化合物γ’ 相Co3(Al, Me)组成 (其中Me为合金元素W、Mo、Ta)，γ’相位于γ相界。1350 ℃/8 h固溶+800 ℃/100 h时效处理的4Mo合金γ相中均匀析出了与之共格并规则排列的立方形γ’相Co3(Al, Me)，γ’相尺寸为200~300 nm；9Mo合金析出大量胞状和针状的к-Co3Mo相以及少量的γ’相。1350 ℃/8 h固溶+900 ℃/100 h时效处理时4Mo合金的γ/γ’共格组织中也析出微量针状к-Co3Mo相，而9Mo合金中的针状相明显粗化。4Mo合金的高低温抗拉伸强度与塑性均高于9Mo合金，合金在600 ℃以上发生反常屈服

Abstract:

The effects of Mo addition and aging temperatures on phase constitution, microstructure and room/high-temperature mechanical behavior of the Co-9Al-xMo-(9–x)W-2Ta-0.02 B alloys (x = 4, 9, referred as 4Mo and 9Mo alloy hereafter) prepared by arc-melting were investigated. Results show that the as-cast alloys are composed of Co-base solid solution γ phase and intermetallic Co3(Al, Me) compound γ’-phase, where Me stands for W, Mo and Ta. The γ phase is the matrix and the γ’ phase distributes on the grain boundaries of the γ matrix. While after 1350 °C/8 h solution and 800 °C/100 h aging, the cubic γ’ phase with a size of 200~300 nm homogeneously precipitates on the γ matrix for the 4Mo alloys. As for the 9Mo alloy, however, the microstructure is significantly changed, and there are a large number of needle-like and cellular к-Co3Mo precipitates besides a few cubic γ’ precipitates. After 1350 °C/8 h solution and 900 °C/100 h aging, a few of the needle-like к-Co3Mo precipitates appear in the 4Mo alloy, while the needle-like к-Co3Mo precipitates in the 9Mo alloy are coarsened. The 4Mo alloy presents excellent tensile mechanical properties, better than the 9Mo alloy at room and high temperature, and both alloys exhibit yield stress anomalies at temperatures above 600 °C