以4种不同Ni含量(15%~45%, 原子分数)的新型γ′相强化Co-Al-W基合金为研究对象, 通过时效与高温热处理显微组织分析以及显微硬度测试, 研究了Ni对相转变温度、g /γ′两相组织演变、γ′相高温溶解行为和显微硬度的影响. 结果表明: 随着Ni含量的增加, γ′相溶解温度升高, 固相线温度未发生明显变化. 4种合金经900 ℃, 50 h热处理后, 基体均为γ/γ′两相组织; 随着Ni含量的增加, γ′相形貌由立方形逐渐向近似球形转变, γ′相体积分数不断降低. 经300 h长时间热处理后, 合金的γ′相形貌没有明显改变, γ′相体积分数出现不同程度的降低. 对900 ℃, 300 h热处理的合金进行970~1060 ℃高温处理后, γ′相体积分数随着热处理温度的升高而逐渐减少, 并最终全部溶解而消失; 低Ni含量(15%和25%)合金和高Ni含量(35%和45%)合金的γ′相形貌分别转变为球形和立方形. 900 ℃, 50 h和300 h显微硬度测试结果表明: 随着Ni含量的增加, 合金的硬度降低; 热处理时间的延长使合金的硬度小幅增加.

The influences of Ni on the phase transformation temperatures, γ /γ′ two-phase microstructural evolution, γ′ dissolution behavior and microhardness have been investigated in four Co-Al-W base alloys containing various Ni contents (15%~45%, atomic fraction). The results show that the γ′ solvus temperatures continuously increase and the solidus temperatures are nearly unchanged with increasing the Ni content. The γ/γ′ two-phase microstructure is generated in four experimental alloys after the heat treatment at 900 ℃ for 50 h, whereas the γ′ morphology changes from cuboidal to nearly spherical and the γ′ volume fraction reduces as the Ni content increases. When prolonged heat treatment at 900 ℃ for 300 h is employed, no significant change in the γ′ morphology is observed in four experimental alloys but the γ′ volume fraction decreases to different degree as a function of Ni concentration. High temperature treatments at 970~1060 ℃ are conducted after experimental alloys are heat treated at 900 ℃ for 300 h. In the high temperature range, the dissolution of the γ′ phase is more pronounced as the temperature elevates, whilst the γ′ morphology becomes spherical and cuboidal in alloys containing the low and high levels of Ni, respectively. The microhardness results of the experimental alloys after heat treatment at 900 ℃ for 50 h and 300 h indicate that the microhardness is lowered in alloys with higher Ni content, but it increases as the heat treatment time is prolonged.