Simulated Effects of Dynamic Recrystallization on Residual Stress During Laser Shock Peening of Ti6Al4V

While microstructure changes due to dynamic recrystallization (DRX) have been experimentally observed during laser shock peening (LSP) treatment, limited work exists to date on simulating the effects. Simulating the LSP process while capturing DRX presents a major challenge due to the intense, nanosecond-scale shock wave propagation and associated high strain rates that necessitate continually updating grain boundaries and localized material properties. Presented is a coupled cellular automata-finite element (CAFE) modeling framework that is capable of predicting DRX as well as its influence on the residual stress field arising from an LSP treatment on titanium alloy Ti6Al4V. The modeling framework includes provisions to predict both continuous DRX (cDRX) and discontinuous DRX (dDRX). For an experimentally determined initial microstructure and specific LSP process parameters the final state of residual stress predicted by this CAFE model on the Ti6Al4V sample shows substantially increased local variation in the compressive stress field as compared to the case when DRX is not considered. The predicted residual stress variation is particularly evident within the vicinity of the specimen surface wherein the majority of DRX, dominated in this case by the mechanism of cDRX rather than dDRX, is also experimentally observed to occur.