Macroscopic and microscopic evolutions of a shot-peened layer during isothermal recovery

The present study deals with the recovery of work-hardened layers, which ar e often encountered in mechanical parts. Two simple cases are studied for t he 38Cr4Mo steel: the shot-peened layer of semiinfinite bodies and a ground surface. The latter case is applied to in situ tensile samples using the g old microgrids technique developed at PMTM Laboratory in order to determine some possible dimensional changes. Both work-hardened layers show the exis tence of macroscopic straining during the recovery. For the only shot-peene d layer, a phenomenological study provides the evolution of the residual st resses and the integral breadth depth-profiles using X-ray diffractometry. A method is proposed to determine the recovery strain field from the residu al stresses evolution. As the only possible strain on a semi-infinite body lies along the normal axis to the surface, calculated recovery strains are compared with the dimensional measurements. On the microstructural viewpoin t, the modified Warren-Averbach's analysis is quickly:presented and is perf ormed to analyze the X-ray peak broadening through the affected layer of a shot-peened sample. Several corrections and deconvolution calculations of t he X-ray profiles finally lead to,the second and third types of broadening effects and their microstructural interpretations.