Microstructure and mechanical properties of Zn25Al3Cu based composites with large Al2O3 particles at room and elevated temperatures

Microstructures and compressive properties of Zn25Al3Cu alloy and Zn25Al3Cu/Al2O3 particulate composites with large reinforcing particles (250 mu m) were examined. The composites were obtained by the compocasting technique through infiltration of 3, 8 and 16 wt.% Al2O3 particles into the semi-solid metal matrix. The influence of temperature in the range from 70 to 170 degrees C on compressive yield strength of the matrix alloy (as-cast and thixocast Zn25Al3Cu alloy) and the composites was investigated. Above 70 degrees C compressive yield strength of all materials decreases, but the rate of decrease is different for the matrix alloy (as-cast and thixocast) and composites. It was found that the abrupt decrease in compressive yield strength of the matrix alloy occurred at temperatures higher than 70 degrees C, whereas composites retained relatively high values of compressive yield strength till the end of the testing temperature range regardless of the amount of reinforcing particles