连续冷却过程中的相变本构方程

Phase Transformation Constitutive Equations during Continuous Cooling

如何有效地预测在不同工艺条件下材料的微观结构和力学性能,是许多钢铁公司非常关注的重要课题之一。以连续冷却过程中的自由能理论为基础,成功地开发出一套在连续冷却过程中统一的相变本构方程。该本构方程可用来预测钢材在不同的冷却速度下从奥氏体到铁素体、珠光体或贝氏体的开始转变点和结束转变点,同时还可用来预测各相转变的体积分数。利用优化算法通过缩小试验数据和预测数据之间的误差来确定本构方程中的材料常数,得出DINSAE5140钢种相变本构方程的模型参数,并且利用该相变本构方程对DINSAE5140钢种的相变过程进行详细地研究。研究结果表明,利用所开发的模型参数得出的预测连续冷却转变(Continuous cooling transformation,CCT)曲线和相变过程中各相的转变体积分数与试验数据非常一致,该统一的本构方程的建立为预测相变过程提供了一种有效的方法。

How to effectively predict the effect of different process conditions on microstructure and mechanical properties is one of important tasks that many iron and steel companies are rather concerned about. On the basis of the theory of free energy during the continuous cooling process, a set of unified phase transformation constitutive equations are firstly developed to predict the start and the finish of phase transformation from austenite to ferrite, pearlite or bainite and volume fraction of each phase for different cooling processes. Optimization techniques are used for the determination of material constants within constitutive equations b y minimizing the errors between experimental and predicted data. The material constants of the phase transformation constitutive equations are determined for DIN SAE 5140 steel. The phase transformation of DIN SAE 5140 steel is researched in detail. Good agreement is obtained between the predicted and experimental continuous cooling transformation （CCT） diagram and volume fraction of DIN SAE 5140 steel. This unified constitutive equation is an effective tool to predict the phase transformation process.