On the microstructural, mechanical, damping, wear properties of magnesium alloy AZ91-3 vol. % SiCP-3 vol. % fly ash hybrid composite and property correlation thereof

Abstract

A combination of hard (SiC_P) and soft (fly ash) particulate reinforcements could be a strategy to enhance combination of multiple properties of Magnesium and its alloys which otherwise suffer from low stiffness, low wear resistance, and many other critical properties. However, at present a comprehensive and robust map correlating different properties in particle-reinforced composites is much lacking. In this work, an industrial grade AZ91 magnesium alloy reinforced with hard SiC and soft fly ash particles (with 3 vol. % each), has been prepared using stir casting followed by hot extrusion at 325 ${}^{\circ }$${}^{\circ }$C with a ratio of 21.5. Microstructure of the hybrid composite was characterized using optical and scanning electron microscopes. The composite exhibited a reduction in average grain size from 13.6 to 7.1 µm, concomitantly an increase in Vickers hardness from 73 to 111 H_V. The tension-compression yield asymmetry ratios of the unreinforced alloy and hybrid composite were 1.165 and 0.976, respectively indicating higher yield strength for the composite under compressive load. The composite exhibited 76% improvement in damping capacity under time sweep mode, and 28% improvement at 423 K under temperature sweep mode. The tribological characteristics of the composite under dry sliding conditions at sliding speeds and loads in the range of 0.5 to 1.5 m s^-1 and 10 to 30 N, respectively showed higher wear resistance than the unreinforced alloy. The composite showed 23% improvement in sliding wear resistance at a load of 20 N and a speed of 1 m s^-1. Finally, efforts have been made to understand the influence of one property on the other by developing statistical property correlation maps from the properties obtained in this study and from the literature. These maps are expected to help in the design of hybrid Metal Matrix Composites for a variety of targeted applications in different sectors.