Thermal Relaxation Behavior of Residual Stress and Microstructure in Shot Peened S30432 Steel at Elevated Temperatures

The thermal relaxation behavior of residual stress and microstructure at elevated temperatures in S30432 austenite steel after shot peening was investigated by X-ray residual stress analyzer. The effect of the exposure time and the applied temperature on the residual stress and microstructure relaxation was particularly analyzed and discussed. A significant decrease of the residual stress values and peak breadth was observed in the first period of exposure time, followed by slowing down and then stabilization. It was also observed that a higher applied temperature produced greater relaxation. The relaxation behavior could be described by Zener–Wert–Avrami function. The thermal stability of microstructure was higher than that of the residual stress. Both of the activation enthalpy of residual stress and microstructure relaxation were higher than that of iron self-diffusion in γ-Fe.