应力作用下的贝氏体相变动力学模型研究

Study on kinetics model of bainite transformation under stress

贝氏体相变动力学及其模型构建一直是学者们研究的热点。以一种中碳超细晶贝氏体钢为对象,对应力作用下贝氏体相变动力学模型开展详细研究。首先采用van Bohemen和Sietsma提出的贝氏体相变动力学模型对实验数据进行拟合,发现拟合得到的自催化系数小于0,不符合物理规律。主要原因是塑性变形带来了额外形核点,这些形核点作为有利位置被优先消耗,导致形核率随时间延长而降低。基于该机制,对van Bohemen和Sietsma模型进行了修正,在贝氏体形核的原始模型中添加了描述形核率降低的函数g(t),并采用幂函数和指数函数2种形式来定义g(t),最终获得了改进后的贝氏体相变动力学模型。改进后的贝氏体相变动力学模型拟合获得的自催化系数大于0,符合物理规律。此外,g(t)为幂函数时,计算精度更高,模型形式更简洁。

The kinetics of bainite transformation and its modelling have always been a hot research topic.The kinetics model of bainite transformation of a medium-carbon ultrafine-grained bainite steel was studied in detail.Firstly,the kinetics model of bainite transformation proposed by van Bohemen and Sietsma was used to fit the experimental data.It was found that the fitted autocatalytic parameter was less than zero,which did not comply with physical laws.The main reason is that plastic deformation brings about additional nucleation sites,which are preferentially consumed as favorable positions,resulting in a decrease in nucleation rate over time.Based on this mechanism,the van Bohemen and Sietsma models were modified by adding a function g(t)in the original model of bainite nucleation to describe the decrease in nucleation rate.g(t)was defined in two forms:power function and exponential function.Finally,an improved bainite transformation kinetics model was obtained.The autocatalytic parameter obtained by fitting the improved model is greater than zero,which conforms to physical laws.In addition,when g(t)is a power function,the calculation accuracy is higher and the model form is more concise.