Properties of squeeze-cast A6061 aluminum alloy-alumina short fiber composites were examined by the cyclic heat and cool test, and the following results were obtained. Compared with the A6061 aluminum alloy with no addition of fiber and casting composites, extruded composites expand in the direction of fibers arranged with increasing the number of heating and cooling cycle. Conversely, contraction is observed in the transversal direction. The amount of plastic deformation increases when the volume fraction of fiber becomes larger. When composites are heated above the recrystallization temperature, they show a sharp increase in deformation amount because of the void formation, but they show no plastic deformation when they are heated below this temperature. Mechanical properties after cyclic heat test are not affected by the number of heating and cooling cycle. The Young's modulus decreases clearly with increasing the number of cycle, as a result of the increase in internal strain. The internal friction increases with incresing the number of heating and cooling cycle. The increase in internal friction can be attributable to more the effect of void formation around alumina short fibers than the intergranular slip induced by plastic deformation.
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