Martensite transformation in the fatigue fracture surface of a high strength bearing steel

•To model phase change both stress and strain induced phase change are considered.•The effect of phase transformation on crack closure was studied.•Results showed that only a very small amount of RA remained in the crack surface.•Crack faces close at an earlier stage when there is a phase change. Phase transformation of retained austenite (RA) to martensite was studied considering both stress and strain induced transformations during fatigue crack propagation. X-ray diffraction measurements, performed on the fatigue crack surface obtained through push-pull experiments, showed that almost all RA in the fatigue surface transformed to martensite. A material model that can simulate the phase change including nonlinear isotropic and kinematic hardening behaviors and nonlinear elasticity was used to simulate the fatigue crack growth. Numerical results showed that only a very small amount of RA remained in the crack surface, which agreed with the X-ray diffraction measurements. The effect of phase transformation on crack closure was studied and it was observed in the FE simulations that the crack faces close at an earlier stage when phase change has been taken into account than when it is absent.