In situ multiaxial loading during neutron diffraction tests were undertaken on a low-alloyed Quenched and Partitioning (Q&P) Transformation Induced Plasticity (TRIP) Bainitic Ferrite (TBF) steel with dispersed austenite particles. The effect of stress triaxiality on the evolution of the deformation-induced martensite is investigated under uniaxial- and equibiaxial-tension as well as tension/compression with a ratio of −1:6. It is shown that transformation is not a monotonic function of stress triaxiality; the amount of deformation-induced martensite is similar under uniaxial and equibiaxial tension but it is significantly smaller under tension/compression. The transformation kinetics are modeled using a recently developed kinetic model that accounts for the stress state and the stability and size of the austenite particles. The larger austenite particles transform first and the mean volume of the austenite particles decreases with increasing strain; the decreasing austenite particle size impedes the phase transformation as the deformation proceeds. It is concluded that stress triaxiality alone cannot account for the differences in the transformation kinetics between different loading states and that the number of potential nucleation sites depends on the stress state.

在具有分散奥氏体颗粒的低合金淬火和分配（Q＆P）转变诱导塑性（TRIP）贝氏体铁素体（TBF）钢上进行中子衍射测试期间的原位多轴载荷。研究了在单轴和等双轴拉伸以及比例为-1：6的拉伸/压缩条件下，应力三轴性对形变诱发马氏体演变的影响。结果表明，相变不是应力三轴性的单调函数。在单轴和等双轴拉伸下，形变引起的马氏体的量相似，但在拉伸/压缩下，则明显减少。使用最新开发的动力学模型对转变动力学进行建模，该动力学模型考虑了应力状态以及奥氏体颗粒的稳定性和尺寸。较大的奥氏体颗粒首先发生转变，并且奥氏体颗粒的平均体积随应变的增加而减小；随着变形的进行，奥氏体粒径的减小阻碍了相变。结论是，仅应力三轴性不能解释不同载荷状态之间转变动力学的差异，并且潜在成核位点的数量取决于应力状态。