Microscopic Response of TRIP Steels to Prestrain During Plastic Deformation

In order to uncover the mechanism of elastic modulus degradation during plastic deformation, uniaxial tensile test of transformation-induced plasticity (TRIP) steels under different prestrain levels was carried out. The real elastic modulus unloaded at each prestrain was calculated by linearly fitting. The microstructure evolution with plastic strain and the fracture morphology were monitored by using a scanning electron microscope (SEM). Dislocation density and its distribution were detected under a transmission electron microscope (TEM). Microscopic mechanism of the elastic modulus degradation of TRIP steels was discussed in detail. Experimental results indicated that the investigated TRIP600 steel was of severe elastic modulus degradation during plastic deformation. The new-born martensite distributed among the retained austenite, resulting in the combination of good ductility and high strength for TRIP steels. It was the change of dislocation movement that induced the variation of atomic binding force and finally led to the variation of elastic modulus.