A framework for predicting residual mechanical response fields for laser powder bed fusion at the polycrystalline length scale

Abstract

A framework is developed to directly model the effect of processing parameters utilized during laser powder bed fusion additive manufacturing (LPBF AM) on material thermomechanical response during solidification in order to predict residual stress and strain development at the microstructure-resolved polycrystalline length scale. Specifically, a workflow is established where the processing parameters serve as input to a cellular automata finite element (CAFE) model that simulates the microstructure solidification evolution via a thermally driven empirical solidification law. The CAFE’s output microstructures serve as representative volume elements which are input to a Multiphysics finite element solver, which solves the thermally driven mechanical response during solidification based on the crystal plasticity finite element formulation. A model validation study is presented, which demonstrates that the modeling framework accurately predicts various features of intragrain misorientation when compared to electron backscatter diffraction data of an LBPF 316L thin wall part built using a GE/Concept Laser M2 SLM system. Following model validation, four variations of processing parameters are chosen to investigate the influence of scan strategy and laser scan velocity on the manufacturing of an LPBF 316L thin wall. Also included is an analogous simulation that treats the microstructure as isotropic and homogeneous, which allows for quantifying the contribution of microstructural heterogeneity on residual stress and strain distribution and magnitudes. Correlations between processing parameters, temperature fields, texture and grain morphology, and the resulting as-built mechanical response are determined and discussed. The current research has the potential to provide valuable insights and guidance for designing AM build conditions to optimize residual mechanical response together with grain structures and textures.