Dynamic Recrystallization in Laser Impact Welding Driven by Surface Morphology

Abstract Laser impact welding (LIW) is a high-speed, small-scale, solid-state metal joining process in which a thin flyer collides with a target, producing localized severe deformation and heating that could activate dynamic recrystallization (DRX). Although DRX has been studied in other high-strain-rate impact processes, its systematic investigation in LIW is limited. This work examines predicted DRX activity in LIW, factors leading to its occurrence, and the influence of the flyer and target surface roughness. DRX evaluation is important since microstructural refinements during impact ultimately affect strength of the welded interface. A Eulerian numerical model is formulated to determine strain, strain rate, temperature, and related fields during LIW based on a Johnson-Cook flow-stress model coupled to a Mie-Grüneisen equation of state to account for strain, temperature, and shock-pressure effects. DRX is evaluated via a post-processing analysis based on the Zener-Hollomon parameter and Johnson-Mehl-Avrami-Kolmogorov relations. Two surface morphology interface conditions are examined, including idealized smooth flyer/target surfaces and experimentally measured rough surfaces. Results show that the rough flyer/target interfaces produce greater local deformation and temperature rise, leading to increased DRX and more refined grains. The temporal sensitivity to local strain and temperature variations highlights a limitation of post-process DRX predictions and demonstrates a need for fully coupled microstructure simulation. This study lays the foundation for predicting and understanding DRX in LIW and suggests that surface morphology plays a critical role in the associated DRX behavior.