Surface hardening analysis for shot peened GH4720Li superalloy using a DEM-FEM coupling RV simulation method

A systematic study was performed to analyze the surface hardening of shot-peened GH4720Li superalloy by combining experiments and numerical simulations. Firstly, it was proved that fine grain strengthening (FGS) and work hardening (WH) are two main strengthening mechanisms of the hardened layer for the plate specimen after shot peening (SP). Then, in order to improve the simulation efficiency, a coupled discrete element method-finite element method model (DEM-FEM) was integrated into the representative volume model to obtain strength distribution quantitatively. The simulation of grain refinement was realized through the dislocation density evolution equation and the degree of WH was characterized by the equivalent plastic strain. Motived by the Vickers hardness test principle, a novel expression between strength and hardness was finally deduced considering both WH and FGS mechanisms, based on which the hardness distribution was evaluated after SP treatment. The hardness by the numerical framework revealed a good agreement with the experimental observations.