An elastic-visco-plastic deformation model of Al–Li with application to forging

Abstract

Recent alloy developments have produced a new generation of Al-Li alloys that provide not only weight savings, but also many property benefits such as excellent corrosion resistance, good spectrum fatigue crack growth performance, a good strength and toughness combination and compatibility with standard manufacturing techniques. The forging of such alloys would lead to mechanical properties that closely match the aircraft engine requirements including lower weight, improved performance and a longer life. As a result, detailed analyses need to be performed to determine which material properties are best suited for a specific structure and how to achieve the required mechanical and damage tolerant properties during material processing. We developed an integrated physics-based model for prediction of microstructure evolution and material property prediction of third-generation Al-Li alloys. In order to develop such a model, an elastic-plastic crystal plasticity model is developed and incorporated in finite element software (ANSYS). The model accounts for microstructural evolution during non-isothermal, non-homogeneous deformation and is coupled with the damage kinetics. Our model bridges the gap between dislocation dynamics and continuum mechanics scales. Model parameters have been calibrated against lab tests including micropillar in-situ simple compression tests of Al-Li alloy 2070. Numerical predictions are verified against the lab results including stress-strain curves and crystallographic texture evolution.

Multi-scale computational modeling of lightweight aluminum-lithium alloys

“…An intermediate step to build the multi-scale model is to find the slip system parameters of the alloy using the available experimental data in Refs. [12], [13]. The used slip system hardening model is given in Eq.…”

“…The experimental data presented in Refs. [12], [13] is used to compare the simulated compression stress-strain curve and microstructural textures. The objective function of the slip system parameters determination problem is defined as the minimization of the difference between the experimental (presented in Refs.…”

“…The objective function of the slip system parameters determination problem is defined as the minimization of the difference between the experimental (presented in Refs. [12], [13]) and computed compression stress-strain curves to calibrate the CP model using Sequential Quadratic Programming (SQP) algorithm. The multi-scale simulation is performed for a plane strain compression mode using a randomly oriented initial texture assumption.…”

“…The given parameters in Table 1 lead to the compression stress-strain curve that is compared to the presented experimental data (Refs. [12], [13]) in Figure 2.…”

“…The slip system parameters of the lightweight Al-Li 2070 alloy are not openly available in the literature. Therefore, the slip system parameters of the alloy are identified by performing an optimization on the multi-scale computational model to minimize the difference between the simulation outputs and the available experimental data for the Al-Li 2070 alloy in the literature [12], [13]. This leads to an inverse problem that is solved with a gradient-based optimization strategy utilizing sensitivities computed with multi-scale continuum sensitivity method (MCSM) [5].…”