Tribological behavior of hybrid Aluminum-TiB2 metal matrix composites for brake rotor applications

This research investigates the feasibility of hybrid aluminum metal matrix composites (MMC) incorporating TiB₂ particles 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 A206 aluminum 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 higher proportions of ex-situ particles demonstrated increased wear resistance compared to those solely composed of in-situ particles, control specimens without TiB₂, and conventional cast iron counterparts. The lowest wear rate for the hybrid composites sliding against phenolic brake pads was 1.1 × 10⁻⁵ mm³/Nm, signifying a 3-fold reduction relative to cast iron sliding against the same pads. Wear analysis elucidated distinctive mechanisms within the hybrid composites, characterized by mild fragmented abrasive wear, adhesive wear, and plastic deformation, accompanied by the formation of an intermixed tribo-oxide layer.