一部分がSiC 粒子とAl_2O_3 ウィスカで強化されたAl 鋳造合金の強度評価とフラクトグラフィ

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In this paper, fracture mechanisms under monotonic and cyclic load and its stress distribution of an aluminum cast alloy locally reinforced by SiC particles and Al2O3 whiskers are investigated experimentally and numerically. The material is monotonically and cyclically deformed to failure at room temperature. The fracture origin and the fracture path are investigated on the fracture surfaces. The fracture occurs in the reinforced part under both monotonic and cyclic loads. SEM analysis of the fracture surface shows that the fatigue fracture is controlled by the fracture of coarse Al_2O_3 whiskers. On the other hand the static fracture (monotonic loading) shows that the fracture mechanism is the combination of reinforcing particle fracture and interfacial debonding between reinforcing ceramics and matrix metal. The stress distributions around the boundary between the reinforced part and unreinforced part are calculated based on an inclusion array model considering the microscopic inhomogeneous effects. Both the experimental results and the finite element simulation results show that the critical location for fracture is changed by the external stress level which controls the local stress distribution through plastic constraint between reinforcing particle and matrix alloy.
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