The phase evolution and Mo mass fraction variation law when Hastelloy C-276 thermally aged at 550, 750, 800℃ for different time were studied. The results show that the carbide is precipitated along grain boundary for short aging time, and the Mo mass fraction firstly decreases to a minimum value about 6％ (mass fraction) with carbide precipitation, then increases with aging time duration. Since the Mo content in nickel-based corrosion resistant alloy is vital to the alloy’s resistance ability, the carbide precipitation process and Mo mass fraction variation near grain boundary (GB) were simulated according to Thermo-Calc calculation, John-Mel transformations kinetics and Fick second diffusion law. The comparison results between the simulated and measured mass fraction of Mo are in good agreement, this signifies that the Mo mass fraction distribution near GB can be predicted by the model presented in this work. Based on simulation results, proper heat treatment conditions for this alloy can be proposed according to the requirement of Mo content in the service corrosion environments.%研究了Hastelloy C-276在550,750,800℃等温时效不同时间后的相析出及晶界附近Mo的质量分数变化规律,结果表明:M6C型碳化物在较短时间内会沿晶界析出,且随碳化物的不断析出晶界附近Mo的质量分数会不断降低直到某一最小值(约为6%),然后开始升高.由于镍基耐蚀合金中Mo元素含量对其耐蚀性能有重大影响,因此本工作利用Thermo-Calc热力学计算结果,结合John-Mel恒温转变动力学及菲克第二定律模拟计算了不同热处理制度下的碳化物析出量及晶界附近Mo的质量分数变化规律.模拟结果表明晶界附近Mo的质量分数计算值与实验测量值基本吻合,这说明利用本模型可以预测该合金在不同热处理制度下晶界附近Mo的质量分数分布.利用上述模拟结果,也可以为该合金在不同应用环境下制定相应热处理工艺来避免其由于晶界贫Mo所出现的各种腐蚀失效问题.
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