Modeling Ti-6Al-4V using crystal plasticity, calibrated with multi-scale experiments, to understand the effect of the orientation and morphology of the α and β phases on time dependent cyclic loading

Classically, crystal plasticity modeling has used a range of constitutive equations, in which the incorporation of additional physics-based relationships typically results in additional model parameters. These additional parameters need to be reliably calibrated, which often necessitates the use of a range of experimental data acquired at multiple length scales. In this work, a crystal plasticity based finite element (CPFE) model for a dual-phase Titanium alloy, Ti-6Al-4V, is developed. The alpha and beta phases of the microstructure are explicitly modeled. The model is calibrated using a systematic optimization routine and experimental data that consist of macroscopic stress-strain curves coupled with lattice strains on different crystallographic planes for the two phases. These experimental data were obtained from in situ high energy X-ray diffraction experiments for multiple material pedigrees, with varying crystallographic orientation distribution and beta volume fractions. Depending on the thermomechanical-processing route and the heat treatment used to manufacture the alloy, Ti-6Al-4V can exist in a wide number of microstructural forms, which often results in the alpha and beta phases either having well aligned slip systems (following the Burgers orientation relationship (BOR)) or possessing no alignment of the slip systems across the interphase boundary (not following the BOR). In this study, the fully-calibrated CPFE model is used to gain a comprehensive understanding of the deformation behavior of Ti-6Al-4V, specifically, the effect of microstructures that follow the BOR (or not) on time-dependent cyclic loading (including the effects of dwell hold times).

Automated summary

Crystal plasticity modeling of a dual-phase Titanium alloy, Ti-6Al-4V, is conducted in this study using a CPFE model calibrated with experimental data. The study provides insights into the deformation behavior of Ti-6Al-4V under different microstructural conditions.