Synthesis of in-situ aluminum matrix composite using a new activated powder injection method

Abstract

In the present study, in-situ Al matrix composites containing alumina particles were synthesized by a new method that involved injection of an activated powder mixture into the molten aluminum, which was subsequently squeeze cast to minimize its porosity. The activated powder mixture was prepared by milling of powders of commercially pure aluminum and zinc oxide for a predetermined time. Milling for 60 minutes led to optimum activation of the reactant powders. Such activation reduced the reaction temperature from above 1000 °C to about 640 °C. Microstructural characterization studies revealed the formation of submicron size alumina particles with near equiaxed morphology and good particle/matrix interface. The composite specimen synthesized using the activated powder injection (API) method exhibited higher hardness, greater yield and tensile strengths, and lower elongation when compared to the monolithic specimen of similar composition. This article places particular emphasis on explaining the uniqueness of the processing methodology used in this study for synthesis of in-situ Al/Al2 O3 composites. © The Minerals, Metals & Materials Society and ASM International 2008.