A mesoscale modeling framework to predict the microstructural evolution at the scales of laser shock experiments

Short-pulsed lasers enable the investigation of the dynamic response of metals at extreme strain rates of loading. The typical experimental setup to study the dynamic response of metals using lasers uses rear surface velocity profiles to understand the loading stresses generated, and in situ characterization using X-ray diffraction (XRD) enables the real-time investigation of microstructure evolution. However, one of the long-standing challenges in interpreting the experimental results is quantifying the defect/phase fractions or the evolution of hydrodynamic instabilities. As a result, current efforts focus on developing materials modeling methods to predict microstructure evolution during the interaction of lasers and improve the interpretation of experimental diffractograms. This manuscript aims to demonstrate the capability of a newly developed hybrid mesoscale-continuum method to accurately capture the laser energy absorption, the electron-phonon coupling behavior, and the related distribution of temperatures and pressures in the sample at the experimental time and length scales. The capability is developed by combining the mesoscale Quasi-Coarse-Grained (QCGD) method with a continuum two-temperature model (TTM) to model the material response at the length and time scales of in situ laser shock experiments. The QCGD-TTM simulations are able to predict the laser-induced kinetics of melting and the evolution of the solid-liquid interface to quantify the solid/liquid/ablated fractions. The QCGD-TTM simulations are able to correlate the phase fractions with the corresponding rear surface velocity profiles and the temperature and shock pressures generated and can complement the interpretation of results in laser shock experiments.