Abstract

The influence of the semi-solid solidification production parameters (shear rate and agitation time) and the concentration of reinforcing particles on the microstructure formation and mechanical properties of a 520 aluminum alloy reinforced with Al 2O 3particles was investigated. Depending on the content of reinforcing particles and the stirring conditions different rosette structures were formed. The type of wear mechanism (delamination or adhesion) depends on the size of the rosettes and the distribution of Al 2O 3 reinforcements. Best mechanical properties were obtained for metal matrix composites reinforced with 12 wt% of Al 2O 3stirred at a shear rate of 2100 s -1 for 1800 s. These samples showed tensile strength and yield stress similar to the commercial A520 alloy. The hardness and wear resistance were improved by the addition of Al 2O 3 particles, meanwhile the elongation to fracture was reduced. © 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.