Establishment of Prediction Method of Nano-size Precipitates Sequences at High Temperatures for Long Term

用系统自由能法预测了18Cr-8Ni奥氏体钢中M&lt；23&Gt；C6碳化物和Sigma相的析出。计算了不同微结构体系自由能谱的化学自由能、界面能和弹性应变能。从最小最大能量路径出发，从理论上预测了两种沉淀物的析出起始曲线。对304H型钢的计算曲线与实验结果吻合较好，表明系统自由能法适用于预测耐热钢的组织演变。

The system free energy method was applied to prediction of the precipitation of M_<23>C_6 carbide and sigma phase within grains in 18Cr-8Ni austenitic steels. The chemical free energy, the interfacial energy and elastic strain energy were estimated for the system free energy hierarchies of various microstructures. From the mini-mum-energy path, the precipitation initiation curves of both precipitates were theoretically predicted. The calculated curves agreed well with experimental results for Type 304H steels ; this suggests that system free energy method is suitable for predicting the evolution of microstructures in heat-resistant steels.