A Hybrid Mesoscale-Continuum Framework to Model Microstructure Evolution during Laser Direct Drive Experiments

High-power pulsed laser irradiation of metal targets enables the study of material behaviors under extreme temperature and pressure conditions. The deposition of laser energy on a metal generates rapid heating and results in melting, ablation, crater formation, and shock compression, and can be used to investigate phenomena such as spall failure and ejecta formation. This work showcases a novel mesoscale-continuum approach that combines the mesoscale quasi-coarse-grained dynamics (QCGD) method with the continuum two-temperature model (TTM) to model microstructural evolution during the spatial and temporal thermal extremes generated in laser direct-drive experiments at the same time and length scales. The QCGD/TTM enables modeling laser energy absorption by electrons, heat dissipation, and heating of lattice through electro-phonon coupling to predict the laser-induced ablation, melting, shock wave generation, and microstructure evolution. The talk will demonstrate the capability of this framework to model laser direct-drive experiments to investigate microstructure evolution for a choice of laser spot size, 3D beam profile (gaussian and top-hat), and laser fluence. The first virtual experiments are carried out to investigate temperature, pressure, and microstructural evolution in Al targets with a thickness of up to 100 microns subjected to nanosecond laser pulses and investigate the mechanisms of spall failure and ejecta formation The framework allows the use of simulated diagnostic tools (x-ray diffraction, phase contrast, etc) on the generated data, which can enable the design of experiments and interpretation of experimental data.