Deformation and dislocation evolution in body-centered-cubic single- and polycrystal tantalum

Abstract

A physically-informed continuum crystal plasticity model is presented to elucidate the deformation mechanisms and microstructural evolution in body-centered-cubic (bcc) tantalum. We show that our structurally unified modeling framework informed by mesoscopic dislocation dynamics simulations is capable of capturing salient features of the large inelastic behavior of tantalum at quasi-static (0.001 s$^{-1}$) to extreme strain rates (10$^3$ s$^{-1}$) and at 77 K and higher (to 873 K) at both single- and polycrystal levels. Notably, we consider the contribution of the non-Schmid effect at 77 K to capture tension-compression asymmetry. Moreover, we also validated our model for the underlying microstructural evolutions in polycrystal tantalum. Toward this end, we compare the experimental data of texture and dislocation density evolution with our corresponding numerical results, and show that our modeling framework is capable of capturing the important features of polycrystal plasticity. The slip instability analysis in our crystal plasticity model shows that the numerical model reflects physical features of the slip instability widely observed in experiments and dislocation dynamics simulations. Notably, we show that instability is mainly attributed to non-convexity due to strong collinear interaction. Our results at both single- and polycrystal levels provide critical insights into the plastic deformation mechanism for the microscopic and macroscopic responses and their relations in this important class of refractory bcc materials undergoing severe plastic deformations.