Correlation analysis of microstructure evolution on microhardness and residual stress for cutting Ti-6Al-4V titanium alloy

Microstructural variation of material directly affects the macroscopic and microscopic mechanical properties of the machined surface. This research investigates the correlation between microstructure evolution and the variation of microhardness and residual stress for cutting Ti-6Al-4V titanium alloy. Firstly, a 2D customized finite element (FE) model has been performed to predict dynamic recrystallization (DRX) and resultant grain size by implementing modified Johnson-Cook(J-C) constitutive model and Johnson-Mehl-Avrami-Kolmogorov(JMAK) model. Then, orthogonal cutting experiments are conducted to verify the accuracy of the established FE model. The predicted values agree well with the measured values and the average error is 8.94% for average grain size. Finally, microhardness and residual stress along with radial direction are measured. The results of simulation and experiment indicate that both microhardness and residual stress profile present an opposite correlation with average grain size profile under different cutting conditions. The correlation analysis between microstructural variation and macroscopic mechanical properties on the surface further deepens the understanding of the machined surface integrity system.