Influence of precipitation and dislocation density on flow stress characteristics under compression deformation of heat-treated 17-4 PH stainless steel alloy

The strengthening mechanism of 17-4 PH stainless steel is mainly due to the precipitation of copper particles in the martensitic lath matrix. The renowned steel grade possesses an exceptional combination of high strength and excellent corrosion resistance and hence is widely employed in high stress environments. In that case, under external loading, the movement and accumulation of dislocations are influenced by the nature of precipitation. Hence, the present study is based on the impact of precipitation on the dislocation induced hardening during compression of the heat-treated 17-4 PH stainless steel. Room temperature uniaxial compression test was used to evaluate the direct effect of precipitates and the dislocation interaction on the flow stress and strain-hardening behavior under the different heat-treated regime. Microstructural evolution during deformation and its influence on the strain-hardening mechanism were analyzed by optical microscopy (OM), scanning electron microscopy (SEM) and X-ray diffraction (XRD). A semi-empirical model was adopted to quantify the role of precipitate nature on the strain-hardening rate. The evaluated normalized microstrain and dislocation density from the XRD analyses were used to explain the observed variation in the mechanical property. Coarse particle precipitation was found to greatly affect the strain-hardening behavior of the steel alloy during compression deformation.