Analysis of dynamic elastic properties of SiC/Al metal matrix composites using Resonant Ultrasound Spectroscopy

Abstract

The effects of SiC reinforcement on the elastic constants of SiC/2124 Al composites were investigated by resonant ultrasound spectroscopy (RUS). Orientation distribution function(ODF) and Mori-Tanaka model were useful to get the more reasonable initial estimate which increased the accuracy to chracterize the elastic constants. The effects of microstructural factors of reinforcement, such as volume fraction, size, shape and alignment of SiC reinforcement on elastic moduli were analysed. In order to determine the elastic stiffnesses of 2124 Al materials, the resonance frequencies of a rectangular parallelepiped specimen were measured and compared with the calculated resonance frequencies based on the input data of estimated stiffness of a polycrystalline 2124 Al specimen, dimensions and density. The estimated elastic stiffnesses were determined using its orientation distribution function measured by x-ray diffraction (XRD) and the reported elastic stiffness of aluminum single crystal. Through the comparison of the calculated frequencies with the measured frequencies by resonance ultrasound spectroscopy, accurate elastic stiffnesses have been determined by iteration and convergence processes. As the extrusion ratios increased, there are a little reduction on the elastic constants due to an increased recrystalization during hot extrusion process. The effect of SiC reinforcement on the elastic behavior of $SiC_p$/2124Al metal matrix composites (MMCs) was investigated in an effort to develop a high modulus material. The MMCs were processed by a powder metallurgy technique and their elastic moduli were characterized on the elastic modulus and internal friction by RUS. The elastic constants as well as the inverse Q factor($Q^{-1}$) of internal friction were measured as a function of the volume fraction and size of SiC particles. A new concept of effective aspect ratio which combined the concept of average aspect ratio and the alignment of reinforcement was used to ...