Simulation Of Geometry Effect Of Residual Austenite On The Mechanical Behaviors Of Q&P980 Steel

In this work, we use finite element model and Eshelby analytical model to study the strain behavior of Q&P980 steel under uniaxial tensile condition. The Q&P980 steel is a multiphase system including ferrite, martensite and residual austenite. The stress-strain curves have been calculated from these two models. We discuss the relationship between the stress of residual austenite and strain. The effect on transformation induced plasticity (TRIP) and the stress-strain curve by the shape and the volume fraction of the residual austenite has also been discussed.To model TRIP effect, we input a stress-strain curve with TRIP characteristics into the constitutive equation of the finite element model to mimic strengthening effect from the phase transformation of martensite. Based on that, axisymmetric, plane-strain and three-dimensional models has been built. Also the Eshelby mode has been adapted to simulate two types of enhancing particles with their intrinsic inelastic stress-strain responses. By comparing the simulation and experimental results, we validate the reliability of the types of models.The simulation results indicate that the plane-strain model cannot properly response the behavior of the stress-induced phase transformation of martensite during loading, so as not to simulate the right stress-strain curve of Q&P980 steel.The comparison of the stress-strain curve of Q&P980 multiphase steel simulated by Eshelby model and finite element model shows that:both two models are consistent with the experimental results, however, the stress simulation of the reinforced phases modeled by Eshelby is closer to the real situation, while the shape and distribution of the second phase can be accurately simulated by finite element model. It is found that the cylindrical retained austenite can surf more stress than the spherical retained austenite through changing the shape of residual austenite. The cylindrical residual austenite is more conductively to develop the transformation induced by stress.The simulation results provide the quantitative relationship between the microstructure and property of materials and it is a preliminary work to the perspective idea of designing materials from microstructural level.