Reinforcement strategies for producing functionally graded materials by friction stir processing in aluminium alloys

tThe present work addresses the production of aluminium based FGM composites by friction based pro-cesses, namely FSP and a consumable tool approach. Several strategies were investigated, featuring theuse of SiC and alumina reinforcements. These strategies were implemented and surfaces analyzed toevaluate the influence of deposition and processing on particle distribution and homogeneity. Threestrategies were studied: a square shaped groove packed with reinforcement particles, the pre-depositionof a uniform layer of particles prior to FSP with a non consumable tool, and the last one consisted of aconsumable rod in aluminium drilled with holes placed in different positions along a radial line filledwith reinforcing particles. Coatings were examined by optical microscopy, scanning electron microscopy,as well as, hardness testing. The strategies investigated proved to be possible in the production of sur-face layers reinforced with hard materials by FSP in aluminium based alloys. While the pre-depositionof reinforcements directly on plate surface enables the simplest approach to produce composites by FSP,the packing of reinforcements in grooves can increase the composite layer thickness. The consumablerod approach allows depositing composite layers soundly bonded to the substrate while avoiding FSPtool wear.