Microstructural and wear characterization of friction stir processed ZrB2/AA7075 in-situ composites

Abstract

Nanocomposites possess properties which are difficult to achieve in micro/macro composites. In the present study, 2 wt% ZrB2/AA7075 nanocomposites (NC) were fabricated through flux assisted casting and subjected to multi-pass Friction Stir Processing (FSP). The fabricated nanocomposite displayed fine grain structure as compared to as-cast AA7075 due to more number of nucleating sites and sluggish kinetics of reaction mechanism between aluminium and inorganic salts. The FSP of the fabricated nanocomposite led to fragmentation of micro-sized clusters of ZrB2 nanoparticles which resulted in its homogeneous dispersion in aluminium matrix. The FSP of nanocomposite refine the grain structure of aluminium matrix due to dynamic recrystallization. The compositional analysis revealed peaks corresponding to aluminium and ZrB2 which showed that no interfacial reaction occurred between aluminium and ZrB2 particles. The hardness of processed zone was improved significantly due to refinement of grains which hindered the movement of dislocations. Friction and wear analysis of as fabricated and processed nanocomposites showed that abrasion reduced as the number of passes increased whereas chance of delamination increased. © 2019 IOP Publishing Ltd.