Co-Al-W三元合金热处理组织

Heat-treated microstructure of Co-Al-W ternary alloys

研究不同Al和W含量对四种Co-Al-W三元合金的初熔温度、热处理组织和硬度的影响.结果表明:四种Co-Al-W三元合金的固、液相点温度均超过镍基单晶高温合金液相点温度;在1300℃/8h固溶处理后,三种合金均仅得到γ(fcc)单相组织,而高W合金在晶界和晶内均有μ相Co7W6析出;在800℃/100h和900℃/50h时效处理后,四种合金在基体γ相中均析出L12型γ′相Co3(Al,W),其γ+γ′两相组织形貌与镍基高温合金相似;高W(12%)和高Al(12%)合金分别促进了μ相Co7W6和富Al相析出.综合以上结果并结合时效合金的硬度结果,初步确定了含γ+γ′两相组织的合金成分范围.

The effects of Al and W additions on the solidus-liquidus temperature, heat-treated microstructure and hardness of four Co-Al-W ternary alloys were investigated. The results show that the solidus and liquidus temperatures of these Co-Al-W ternary alloys are higher than the liquidus temperatures of Ni-base single crystal superalloys, γ（fcc） single phase existed in the matrix of three alloys after solid solution treatment at 1 300 ℃ for 8 h, while μ phase-CoTW6 was observed along grain boundaries and in grain interiors in the alloy containing high level of W. γ′ phase-Co3 （Al, W） with L12 structure precipitated in the γ matrix of four alloys after aging treatments at both 800 ℃/100 h and 900 ℃/50 h, similar to the microstructure of Ni-base superalloys. High levels of W and Al addi- tions promoted the precipitation of μ phase-CovW6 and Al-rich phase, respectively. Combined with the results of hardness after different aging treatments, the composition range of these ternary alloys containing γ ＋ γ′ two phases was preliminarily determined based on microstructural stability and potential high-temperature mechanical properties.