PNNL

Abstract

This research delves into the feasibility of employing hybrid aluminum metal matrix composites (MMC) with TiB2 reinforcement for brake rotor applications. The composites were produced by incorporating both in-situ submicron-sized TiB2 particles and regular micron-sized TiB2 powders via stir and squeeze casting techniques into a A206 alloy matrix. Systematic adjustments in the fractions of in-situ and ex-situ TiB2 particles were conducted to evaluate their impact on wear behavior and mechanisms. Combination of both particle types allowed composites with up to 10 vol% of reinforcements. Composites with increased proportions of ex-situ particles demonstrate increased wear resistance compared to those solely composed of in-situ particles, control specimens without TiB2, and conventional cast iron counterparts. Specifically, the hybrid composite comprising 2 vol% in-situ + 8 vol% ex-situ TiB2 particles exhibits a wear rate of 1.1 x 10-5 mm3/Nm, signifying a 2.7-fold reduction relative to cast iron. Moreover, wear analysis elucidates distinctive mechanisms within this composite, characterized by mild fragmented abrasive wear, adhesive wear, and plastic deformation, accompanied by the formation of an intermixed tribo-oxide layer. These outcomes underscore the potential of hybrid aluminum MMCs with TiB2 particles to deliver enhanced tribological performance for brake rotor applications.