Synthesis, mechanical and tribological characteristics of Mg/SiC metal-matrix composites

Abstract

In the present study, magnesium based composites were successfully synthesized using innovative disintegrated melt deposition technique (DMD) followed by hot extrusion. Varying amounts of sub-micron SiC particulates (average size of 0.6I?m) were incorporated as reinforcement in magnesium matrix and the composites were subjected to recrystallization heat treatment. Finally, hybrid magnesium composites were synthesized by reinforcing magnesium with Ti particulates along with the sub-micron SiC. The primary objectives of this study are: (a) to examine the feasibility of synthesizing sub-micron SiCP and or TiP containing Mg-based composites using DMD technique, (b) to study the effect of adding various amounts of sub-micron SiC and or Ti particulate reinforcements on the microstructural, thermal, mechanical and surface scratch properties of pure magnesium, and (c) to investigate the effect of heat treatment on the composite properties. Systematic investigations on the microstructure of the extruded samples revealed a fairly uniform distribution of SiC particulates with limited clustering, good interfacial integrity between the reinforcement particulates and the metallic matrix. Mechanical properties of the materials were assessed by conducting macro and micro hardness tests, tensile tests and scratch tests. The results of the microhardness, macrohardness and tensile tests revealed an increasing trend with an increasing amount of sub-micron SiC particulates incorporated in the matrix. Hardness values decreased marginally after heat treatment. Furthermore, the sliding scratch tests revealed that with increasing amount of reinforcement there is an improvement in the scratch hardness. The hybrid Mg/SiC/Ti samples exhibited a significantly superior combination of elastic modulus, 0.2% YS and UTS when compared to pure Mg samples, while the ductility dropped. Fracture analysis was carried out on the tensile fractured surface of monolithic and composite samples using scanning electron microscope.