Characterization of pressure-assisted sintered Al–Si composites

The use of applied pressure in the processing of fiber-reinforced metal matrix composites ultimately plays a critical role on the effectiveness of load transfer in the resulting composites. This study has investigated the fiber degradation effects due to applied pressure in the fabrication of Al-13.5Si-2.5Mg alloy reinforced with Al2O3-4%SiO2 (saffil) short fibers. The conventional, double-compaction reaction-sintering method was used with a compaction pressure of 250 MPa. Fiber deformations and breakage as well as fiber clustering were observed by scanning electron microscopy (SEM) and X-radiography. An electron probe microanalysis (EPMA) of the fractured surfaces of the interface-failed parts showed absence of reaction-zones. Localized fiber-matrix reactions were identified, and this is contributory to the determined low tensile and thermal properties. At the applied pressure, no significant change in tensile properties were observed as additions of the reinforcing fibers were made. A 24% decrease in linear thermal expansion coefficient of the matrix was determined at 1.2 vol. % fiber.