FABRICATION, MICROSTRUCTURES, AND TENSILE PROPERTIES OF MAGNESIUM ALLOY AZ91 SICP COMPOSITES PRODUCED BY POWDER-METALLURGY/

The tensile properties and microstructural evolution of hot extruded A Z91 magnesium alloy with and without reinforcement of SiC particles ha ve been investigated in terms of extrusion parameters, such as extrusi on ratio and extrusion temperature. Also, the effect of SiC particles on the grain size of the matrix in the composites was evaluated using the Hall-Fetch equation. The AZ91 magnesium alloy powders prepared by wet attrition milling from magnesium machined chips were hot pressed w ith and without SIC particles, hot extruded and then solution treated. Microstructural observation revealed that both the composites and the magnesium alloy have fine equiaxed grains due to the dynamic recrysta llisation during hot extrusion. The tensile strength of both materials increased with increasing extrusion ratio, and the strengths of the c omposites were higher than that of the magnesium alloy without reinfor cement. It was found that the tensile strength of both the materials d ecreased after solution treatment, and the decrease in tensile strengt h of the composites was considerably smaller than that of the magnesiu m alloy. From analyses of the microstructures and the mechanical prope rties, combined with examination of the Hall-Perch relationship the re finement of the matrix was primarily responsible for the improvement i n the yield strength of the composites. The grain growth of the matrix was inhibited by the introduction of the SiC particles. (C) 1997 The Institute of Materials.