Microscale deformation behavior of rheocast Al–7Si–0.3 Mg alloy

Abstract

In the present work, microscale deformation behavior, plastic strain localization, and plastic instability of rheocast Al–Si–Mg (A356) alloy have been investigated using micromechanical approach. For this purpose, two-dimensional microscale models (representative volume elements) have been developed using actual microstructure of the cast samples made under three different process conditions. Microstructure of the above-mentioned alloy consists of two different phases, such as aluminum-rich primary phase and silicon-rich eutectic phase. In line with that, composite micromechanical models have been developed to analyze them within the finite element framework. Rheocasting has been performed using cooling slope with two different slope angles of 45° and 60°, and comparison has been made with the conventional cast samples of the alloy that has been cast directly from the superheated molten state. Different boundary conditions have been assumed to perform finite element based simulation, using a popular finite element solver ABAQUS, depending upon the position of representative volume elements on the cylindrical tensile specimen. Under uniaxial tensile loading, ductile failure mode is predicted in the form of plastic strain localization due to incompatible deformation between the phases. This indicates inhomogenity of microstructure that determines the damage initiation process within this material, as there is no damage or failure criterion specified during the finite element analysis. Grain size, shape, and orientation of the primary aluminum phase are found to play a vital role on deformation behavior and failure mode of the materials investigated in this study.