Coupled effects of thermal and micro-damage softening on the initiation of adiabatic shear instability in strongly textured pure tungsten

Previous research has shown that introducing appropriate strong texture components into low-ductility pure tungsten (W) can more readily induce adiabatic shear localization. However, identifying the key factors that drive plastic instability in strongly textured pure W remains a significant challenge, particularly in accurately accounting for the thermal softening effect on the evolution of dynamic instability. In this work, we first investigated the mechanical response, temperature and strain fields evolution of coarse-grained W and as-rolled W under dynamic compression using a “force-heat-deformation” dynamic in-situ synchronous testing system based on split Hopkinson pressure bar. The Taylor-Quinney coefficient of pure W was determined to be about 0.55 at large strains, and the detected temperature rise within the localized shear zone was very limited even after instability occurred. Hence, thermal softening was not the sole factor triggering the adiabatic shear bands (ASBs). Subsequently, meticulous microscopic observations revealed the appearance of interlaminar microcracks along the shear directions prior to dynamic instability. To consider the microscale damage effect on the dynamic instability evolution, we incorporated a damage evolution equation into the crystal plasticity finite element model (CPFEM) to more accurately describe the dynamic instability responses of this strongly textured pure W. By comparing the experimental and CPFEM simulation results, their high consistency indicated that incorporating the damage evolution model significantly promoted shear concentration and the subsequent instability. The coupled effects of thermal softening and micro-damage evolution are the critical factors triggering plastic instability in strongly textured pure W. This work provides a profound understanding of the micro-damage softening effect on the evolution of dynamic instability behavior in metallic materials.