The Abrasive Wear Behavior of In Situ Processed Aluminum Alloy Metal-Matrix Composites

An aluminum alloy, i.e., aluminium-silicon alloy reinforced with particulates of titanium diboride (TiB2) and in situ processed metal-matrix composites can safely be categorized to be an advanced material that has shown much promise for selection and use in the industries spanning structural, automotive, aerospace, and both performance-critical and non-performance-critical end products. This is essentially because of its high strength-to-weight [sigma/rho] ratio and good-to-excellent wear resistance characteristics. These composites tend to exhibit superior wear resistance coupled with good fatigue strength in comparison with the monolithic counterpart at both room temperature and at elevated temperatures. An exothermic reaction between the hexafluorotitanate (K2TiF6) salt, potassium borofluoride (KBF4) salt, and molten aluminum-silicon (Al-Si) alloy results in the production of the TiB2 particulates which is present as the reinforcing phase in the soft aluminum alloy metal matrix. Two volume fractions of the TiB2 particulate reinforcement, i.e., 3 weight pct. and 6 weight pct. were considered for synthesizing test specimens of the composite material. The presence of both titanium and boron in the reinforcing TiB particlesB was confirmed using energy-dispersive X-ray analysis. Study of microstructure of the in situ processed composite specimens revealed a near-uniform distribution of the TiB2 particulates in the aluminum alloy [Al-Si alloy] metal matrix. Mechanical properties and dry sliding wear behavior of the as-synthesized composite materials were studied using a pin-on-disk tribometer. The coefficient of friction (COF) and wear rate were studied with precision under various conditions. The intrinsic mechanisms governing wear and elemental analysis of the wear surfaces of the composite test specimens were established following examination in a scanning electron microscope.