Abstract
Methods for uniform dispersion of graphite particles in Al-Si melts, and mechanical properties and wear resistance of graphite-dispersed Al-Si alloys have been investigated. The weight per cent of graphite varied from 2.1 to 17.4%.
Uniform dispersion of graphite particles was obtained by adding nickel-coated graphite particles into the melts. Gas hole formation during the solidification of the melts was suppressed under a pressure of about 560 kg/cm2.
Two series of graphite-dispersed Al-8%Si and Al-12%Si alloys containing 3%Cu, 0.3%Mg and less than 5.6%Ni were used for the investigation of mechanical properties and wear resistance.
Although the strength and elongation in this alloy system decreased with increasing graphite content, even the alloys containing 17.4 wt% graphite seemed to be capable of industrial use.
Under dry friction, the wear resistance of the alloys increased with increasing graphite content. The wear rate of the alloys containing 17.4 wt% graphite was about 10−8 mm3/mm·kg, which was nearly equal to that under lubricated friction of the graphite-free base alloys. Under lubricated friction, the wear resistance of the alloys increased over the composition range of 5 to 10 wt% graphite. However, the wear resistance decreased in the alloys containing graphite in excess of the amount which gives the maximum wear resistance. It was also found that the graphite content corresponding to the maximum wear resistance increased with increasing strength of the alloys, or with decreasing load in the wear test.
