Synergistic Effect of Ex Situ and In Situ Reinforcements on the Dry Reciprocating Wear Behavior of AA6061-B4C Composite Fabricated Using Varying K2TiF6 Flux Content

This study aims to examine the dry reciprocating wear behavior of stir-squeeze cast AA6061-B4C composites under the synergistic effect of ex situ B4C particles and in situ formed Al-Ti intermetallic phases due to the use of K2TiF6 salt as flux and Mg2Si precipitates formed after T6 heat treatment process. The K2TiF6 flux content in the composites varied between 40 and 100% of a constant B4C content (6 wt.%). The heat treatment consisted of solutionizing at 540 degrees C for 8 h, followed by water quenching and then artificially aging at 180 degrees C for 4 h. While at any applied load, the wear rate decreased with increasing ex situ B4C particle retention, at applied loads more than 20 N, the wear performance deteriorated due to increased fracture and dislodgement of B4C particles. In situ Al-Ti intermetallics were more effective in lowering the wear rate at high applied loads. A mechanically mixed layer (MML) consisting of self-lubricating boron oxide and boric acid was formed in composites with high B4C particle retention, lowering the friction coefficient up to 20 N applied load. However, the friction coefficient increased at a higher applied load of 30 N due to increased peeling off the MML and three-body wear.