Preparation For Aluminum-Graphite Composite By Semi-solid Forming Method And Study On The Frictional Behavior

Aluminum-graphite composite is a very ideal self-lubricating and conducting wearable material for bearing and cylinder liner. In this paper, Aluminum-graphite composite is prepared by the semi-solid casting technology, its microstructure and friction performance is studied as follows:1. The uniform aluminum-graphite composite is prepared by the semi-solid castingtechnology.The aluminum-graphite slurry which is prepared by the electromagnetic-mechanical stirring technology is researched. The linear formula between the solid fraction and the stirring temperature was attained; The relationship between the solid fraction and the size of aggregate graphite is determined and the condition for eliminating macro-segregation of graphite in the solid Aluminum-graphite composite is obtained as follows: when the solid fraction of the composite slurry is above 30%, the macro-segregation of graphite can be eliminated.2. Friction behavior of semi-solid casting Aluminum-graphite composite against 45 steel under dry sliding is evaluated in the pin-on-disc tribological tester. The relationship between friction coefficientμand load N is investigated, quadratic formula is concluded as follows:μ= 0.256+(1.157×10^-4)N+(8.749×10^-7N²The relationship between friction coefficient and friction time have got. The microstructure character of friction surface under different friction time is analysed and the mechanism of friction is confirmed. The results show that when friction time is controlled between 0-40minutes, friction coefficient toboggan as time extends; on the other hand, while time is controlled between 40-120 minutes, descend of friction coefficient goes to be slower, and only a little declining is formal after the 120 minutes, friction coefficient has a steady value of about 0.2763, without change with time.3. The formation mechanism of graphite lubricating film were analyzed in theprocess of friction. The reduction in friction of composites is because of the formation of graphite lubricating film during sliding.