Wear behaviour of planar-random fibre-reinforced metal matrix composites

Abstract

The wear behaviour of δ-alumina fibre-reinforced aluminium–zinc–copper alloy composites produced by squeeze casting was investigated using a pin-on-disc wear machine. Samples of metal matrix composites were tested in the normal and planar-random orientations sliding against a smooth steel counter-surface disc at a fixed speed under different loads without lubrication. Wear surfaces of the MMCs and of their matrix alloy were also examined in a scanning electron microscope. The experimental results showed that the composite exhibited a low wear rate compared to the unreinforced matrix material. The wear rate decreased with an increase in volume fraction of fibre, and increased with increasing load. The optimum wear resistance occurred when most of the fibres were oriented normal to the sliding surface. Scanning electron microscopy of the worn surfaces showed that microfracture of the fibre, and reattachment of a fragmented surface layer in the normal orientation, and large scale microfracture of the fibre, and subsurface delamination were the principal mechanisms of wear in the planar-random orientation composites. Oxidation and partial delamination were predominant in the unreinforced matrix alloy.