Study of Dry Sliding Wear Characteristics of Sillimanite Reinforced Aluminium Alloy Matrix Composites

Abstract

The aim of the present study was to develop light-weight, economical, and high temperature resistant aluminium matrix composites for brake rotor applications. Aluminium matrix composites (AMCs) containing LM30 aluminium alloy as matrix and sillimanite mineral particles as reinforcement were processed using stir casting. Sillimanite particles were taken in three different size range viz. coarse (75 106 µm), medium (32 50 µm), and fine (1 20 µm). Two main categories of AMCs were processed. The first category included single particle size AMCs (SPS) where the matrix material was reinforced with sillimanite particles of one specific size range (coarse, or medium, or fine). The second category included dual particle size AMCs (DPS) where the matrix was reinforced with sillimanite particles of two specific size ranges. For both type of AMCs, the maximum reinforcement level (with uniform distribution of particles with nearly no agglomeration) was 15 wt.% (0 15 wt.%; in step size of 3 wt.%). Further, for DPS composites, a mix of fine and coarse sized particles were reinforced with fine:coarse weight ratio as 1:3, 1:1, or 3:1. For processing of composites, the base alloy was melted and stirred at 630 rpm for 4 5 minutes at 750 . Pre-heated sillimanite particles (heated to 350 ) were added to molten mass at a reduced stirrer speed of 250 rpm. The mixture was stirred at 630 rpm for 10 12 minutes and poured into a cast iron mould. For wear testing, pins of 8 mm diameter were machined as per ASTM G99 standard. EDS analysis of sillimanite particles showed the constitution as SiAl1.8O6.1 which confirmed the purity of sillimanite (Al2SiO5). XRD analysis of base alloy showed presence of aluminium, silicon, and aluminium-copper phases. For AMCs, in addition to these phases, sillimanite and aluminium silicate (Al2Si4O10) phases were also observed. Optical micrographs of base alloy showed presence of eutectic aluminium, eutectic silicon, and large facets of proeutectic (primary) silicon phases.