Tensile properties of randomly oriented short δ-Al2O3 fiber reinforced aluminum alloy composites. I. Microstructure characteristics, fracture mechanisms and strength prediction

Abstract

The tensile properties of short δ-Al2O3 fiber randomly reinforced aluminum alloy composites were characterized. Systems based on three matrix alloys, Al–5.5Zn, Al–5.5Mg and Al–12Si, were prepared to observe and measure the microstructural and mechanical characteristics of squeeze cast short fiber composites, including the orientation and length of short fiber, interfacial bond and micro-hardness of the reinforced matrix. It was found that the orientation and length of the short fibers satisfied the Weibull's and normal distribution, respectively. The micro-hardness values of the reinforced matrix alloys were higher than that of the unreinforced alloys. The interfacial bond differed with the variation of matrix alloy. Based on the microstructural characteristics and in situ tensile observation by scanning electronic microscopy, the fracture mechanisms of the three composite systems were discussed and related to the microstructural characterization. Finally, the tensile strengths of the composites were predicted by the statistical integration average method, based on using the maximum energy criterion for the composite strength. In this way, the prediction accounts for the practical distributions of the fiber orientation and length. The predicted results agree well with the experimental data.