Characterisation studies and mechanical properties on friction stir processed AZ31B with SiC and C nanoparticles to enhancing surface composites

Friction stir processing (FSP) is a solid-state-surface-modification method to enhance the mechanical and microstructural properties of AZ31B magnesium alloy. The introduction of FSP into pre-drilled surface holes and incorporation of SiC and C nanoparticles in the stir zone were done to assess the effect of the nanoparticles on grain refinement and surface mechanical performance. Microstructural analysis showed that SiC nanoparticles dispersed uniformly and this led to the occurrence of considerable grain refinement within the region of processing, but in comparison, carbon nanoparticles dispersed rather non-uniformly. The non-uniform dispersion and lower strengthening in the carbon nanoparticle reinforced region result from severe particle agglomeration caused by the low impact of the Zener pinning mechanism. Weak interfacial bonding between the matrix and carbon nanoparticle limits effective load transfer. The higher hardness and strength in the SiC-reinforced region are due to strong interfacial bonding that enables efficient load transfer from the matrix to the hard SiC particles. Furthermore, SiC particles refine grains and pin grain boundaries, restricting dislocation motion and thereby enhancing strengthening. These findings indicate that the SiC nanoparticles are superior to carbon nanoparticles in terms of enhancing the surface mechanical properties of FSP-processed AZ31B magnesium alloy, which is related to light weight structural applications.