The effect of forging on the properties and microstructure of saffil fibre reinforced aluminum

Abstract

The forging of aluminium and Al/7% Si alloy reinforced with short alumina fibres has been investigated. A deformation of 12% at room temperature was found to reduce the flexural modulus and strength of the composite by over 20% but, with progressively higher forging temperatures, the properties approached those of as-received material. Such trends are related to the extent of fibre breakage and to the formation of pores around fibres. Breakage of fibres was much less in samples forged at high temperature owing to the lower matrix flow stress and a corresponding reduction in load transfer from the matrix, but at temperatures close to the melting point, where the matrix lacked the rigidity for load transfer, fibre—fibre contact during the forging process was a significant factor in fibre breakage. A modified rule-of-mixtures relationship showed that changes in flexural strength with forging temperature could be related to the fibre aspect ratio. Calculated strengths indicated that reinforced metal had a higher flow stress than unreinforced and this is discussed in terms of differences in microstructure.