Influence of Al2O3 fiber reinforcement on the thermal mechanical fatigue behaviour of the cast aluminium alloy AlSi10Mg

Thermal-mechanical fatigue (TMF) tests under total strain constraint were carried out on the cast Aluminium alloy AlSi10Mg - T6, unreinforced and with 15% Al2O3 (Saffil) fiber reinforcement, respectively. The number of cycles to fracture is increased markedly by the fiber reinforcement, especially for maximum cycle temperatures above 250 degrees C. Surprisingly, during TMF cycling higher stress amplitudes are induced in the unreinforced alloy than in the fiber reinforced one. The cyclic softening behaviour observed at both materials is more pronounced for the unreinforced alloy. In tensile tests at 20 degrees C, the unreinforced material revealed a higher 0,2% proof stress than the fiber reinforced one. These results are explained by a magnesium enrichment in the fiber-matrix interface of the compound material which was proved by EDX analyses. According to this, the Mg content of the compound's matrix is lowered and the hardenability of the fiber reinforced material is reduced below the one of the unreinforced alloy.