Kinetic simulations of σ phase precipitation in duplex and hyper duplex stainless steels were carried out by employing mean field approach. For duplex and hyper duplex steels, time-temperature-precipitation (TTP) curves were calculated and compared with experimental results. Thermokinetic predictions confirm that segregation of Cr and especially Mo at grain boundaries of ferrite plays an important role for the nucleation of σ phase in ferrite. This is also reflected by the concentration change of dissolved Mo in σ phase from early nucleation stage to precipitation after long-term isothermal aging of several hours. From the present results, predictive simulations of modified alloy compositions are presented and discussed.

采用均场法对双相和超双相不锈钢中的σ相析出进行了动力学模拟。对于双相和超双相钢，计算了时间-温度-沉淀（TTP）曲线并将其与实验结果进行了比较。热动力学预测证实，在铁素体晶界的Cr尤其是Mo的偏析对于铁素体中σ相的成核起重要作用。长期等温老化数小时后，从早期成核阶段到析出的σ相中溶解Mo的浓度变化也反映了这一点。从目前的结果，提出和讨论了改性合金成分的预测模拟。