Nondestructive Determination of the Elastic Anisotropy in Aluminum–SiC and -Al2O3 Metal–Matrix Composites

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Process control is becoming increasingly important to the high performance applications of aluminum metal–matrix composites. Most processing conditions of metal–matrix composites introduce a degree of anisotropy that results in the directional dependence of material properties. Aluminum alloys reinforced with up to 20 volume % silicon-carbide or alumina particles are examined using ultrasonic velocity measurements. The measurements indicate that these composites are transversely isotropic and thus their elastic properties can be described by the five independent elastic constants C 11, C 33, C 44, C 12, and C 23. Anisotropy parameters are determined assuming either a preferred alignment of the matrix crystallites or a preferred alignment of the reinforcement. Comparing measured and theoretical anisotropy parameters for partially aligned reinforcement or for texture shows that neither is the single contributor to anisotropy in the composite material.