Aging behavior of squeeze cast SiCw/AZ91 magnesium matrix composite

The aging behavior of SiC whisker reinforced AZ91 magnesium matrix composites was investigated with Vickers hardness measurement, differential scanning calorimetry (DSC), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The precipitation process observed in the monolithic alloy was not altered by the addition of SiC whiskers. The composite exhibited an accelerated hardening response compared with the unreinforced matrix alloy. However, the addition of SiC whiskers altered the distribution of the Mg17Al12 precipitates. Mg17Al12 precipitated preferentially at the SiCw-AZ91 interface, with a definite orientation relationship with SiC whisker: (110)(Mg17Al12)//(111)(SiCw), [111](Mg17Al12)//[011](SiCw). The preferential interfacial precipitate decreased the Al content in the matrix, resulting in a decrease in the amount of continuous precipitates. As a consequence, the age-hardening efficiency in the composite was lower. (C) 2002 Elsevier Science B.V. All rights reserved.