On characterizing the mechanical properties of aluminum-alumina composites

The overall response of aluminum-alumina (Al-Al2O3) composites depends strongly on their microstructural characteristics. We study the overall mechanical response of Al-Al2O3 composites experimentally, using Resonant Ultrasound Spectroscopy (RUS) and uniaxial compressive testing. Microstructures of composite with 10% alumina volume content are constructed from the microstructural images of the composite obtained from scanning electron microscopy (SEM). The SEM images of the composite are converted to finite element (FE) meshes, which are used to solve the boundary value problem in order to determine the overall mechanical response of the Al-Al2O3 composite. The responses generated from the micromechanical models are compared with the elastic modulus obtained from RUS and experimental stress-strain curves from uniaxial compression tests. Effects of processing, porosity, alumina content, thermal (residual) stress, and plastic deformation on the overall elastic modulus and response of the composites are also studied. We observed that slightly altering the processing method had a significant effect on the microstructural characteristics and in turn on the overall physical and mechanical properties of the composite. With changes in porosity by 2-3%, the elastic modulus was found to vary by 10-15 GPa approximately. We observed that the elastic moduli of the composites determined from the uniaxial compressive tests are close to those obtained from RUS.