Microstructural study of aluminium-matrix composites reinforced with SiC

Rheocasting, as a semi-solid process, allows the production of aluminium matrix composites at relatively low temperatures (ca. 580°C), thus favouring a reduced reactivity at the reinforcement-metal matrix interface. When one considers the possibility of further processing (such as any treatment involving remelting, even if partial) of the material, this trait allows a more rigorous control of the interfaces. Composite samples have been produced using as matrix an Al-7Si-0.3Mg alloy reinforced with SiC_p (granulometry: 120 μm; V_r = 0.30). These were rheocast at 583°C, followed by compression and subsequent water-quenching. A structural characterisation (optical microscopy and XRD) of the as-received matrix material, as well as of the reinforced and non-reinforced rheocast material was performed. The phases identification will provide a basis for the understanding of the further processing where the rheocast material will be used as a precursor to produce functionally graded metal-matrix composites by centrifugal casting.