A microstructure-based porous crystal plasticity FE model for additively manufactured Ti-6Al-4V alloys

Abstract

Building from a foundation of microstructural characterization, mechanical testing, 3D statistically equivalent microstructural volume elements (SEMVEs), and image-based microstructural modeling, this paper develops an effective crystal plasticity model with porosity evolution for additively manufactured Ti-6Al-4V alloys. Their microstructure is characterized by a complex Widmanstätten morphology containing 12 α lath variants. In this paper, the morphology is parametrized by statistically equivalent ellipsoids, enabling a parametric representation of the α laths in the models. An effective crystal plasticity framework with the parametric representation of the α lath morphology is achieved by identifying the crystallographic relationship of the α laths in relation to the parent β grains from which they have nucleated and developing methods to incorporate a statistical representation of HCP α laths in β grains. The constitutive model for β grains statistically accounts for the size, shape, orientation, and crystallography of all 12 α lath variants. An important contribution is the integration of porosity evolution with the crystal plasticity model. The model is calibrated and satisfactorily validated with results from experiments on additively manufactured Ti-6Al-4V alloys with and without heat treatment. The model can yield important insights into the underlying physics of this relatively new class of materials.