Crystal Plasticity Based Numerical Modeling of Temperature and Strain Rate Dependent Behavior in Mg Alloys

Abstract

This thesis provides a combined experimental and numerical study to explore the mechanical and forming behavior of E-form Plus Mg alloy. For the last few decades, Mg alloys are a key of interest for replacing heavier steel and aluminum car body parts in the automotive industry. Mg alloys are known due to their outstanding mechanical properties. However, the formability of Mg alloys at room temperature needs to be improved. In these regards, E-form Plus Mg was chosen for the study due to the improved formability at room and elevated temperatures. The goal of this work is to enhance the understanding of the mechanical behavior of the material and microstructure-property relationship at various strain rates and temperatures. In these regards, the experimental investigation of mechanical behavior and texture evolution for E-form Plus Mg alloy at various strain rates and temperatures is performed. In order to establish the correlation between mechanical properties of the alloy and temperature, strain rate, an energy-based material model using on Arrhenius-type relation is proposed. The model is incorporated into Taylor-type crystal plasticity framework. This model is used as a predictive tool to obtain the stress-strain response and the texture evolution for E-form Mg alloys at different strain rates and temperatures. The predictive capability is shown by comparison the experimental and simulated data. Next, the developed model is applied to build a linkage between the mechanical response and deformation mechanisms. The activity of various deformation mechanisms at different strain rates and temperatures is obtained. The simulated data were analyzed to understand the influence of temperature and strain rate on mechanical properties and microstructure and texture evolution of E-form Plus Mg alloy. Finally, the developed modeling approach in conjunction with the M-K framework is applied to generate the forming limit diagrams (FLDs) for E-from plus Mg alloy. The simulated results were used to analyze temperature and strain rate effects on forming behavior of the material. The obtained results successfully predict the effect of temperature on FLD. It is shown that a decrease in temperature improves the formability of Mg alloys. However, the models show the inability to capture the strain rate influence on the forming limit curves (FLCs). The analysis of deformation mechanisms is provided to explain the strain rate dependence of the E-form Plus Mg alloy forming behavior.