Experimental investigations on the enhancement of mechanical properties of magnesium-based hybrid metal matrix composites through friction stir processing

Friction stir processing (FSP) is a solid-state processing technique that has unique capabilities like low amount of heat generated, extensive plastic flow of material, achieving very fine microstructure in the stirred region and healing of flaws and casting porosity. FSP offers the ability to locally tailor properties within a structure. It is a method for modifying the mechanical properties of surfaces by means of stirring action of the tool moving against the surface of the material whose properties need to be modified. In this research work, an attempt has been made to investigate the enhancement in the mechanical properties on the surface of magnesium-based metal matrix composites manufactured through stir casting. Silicon carbide (SiC) and aluminium oxide (Al2O3) with a particle size of 20 μm of 5 wt% were used as hybrid reinforcing agent in magnesium matrix material for the composite manufacture. FSP has been done on the surface of the composites to refine the grain sizes of the proposed composite materials. Microstructural studies have been carried out to investigate the grain size variations and observed an appreciable refinement in the grain size from 84 to 7 μm. Three different tool rotation speeds and three different linear movements of the tool were considered as the process parameters. From the experimental outcomes, optimum process parameters were obtained for achieving the fine grain size along with improved hardness values, tensile properties and wear property of the proposed composite material.