Friction And Wear Performance Of Hypereutectic Wrought Al-Si Alloy

The hypereutectic Al-Si alloy is an ideal light high-abrasive material because of many perfect properties such as lightweight, high strength, good wear-resistance, high heat resistance and low thermal expansion. As the conductor rail sectional material, compared with steel aluminum composite materials, hypereutectic Al-Si alloy has advantages in the respect such as economy, service life, production technology, transportation and installation and electrical conductivity. Therefore, hypereutectic Al-Si alloy has a very attractive application prospect. In this paper, we take the Al-16Si, Al-16Si-0.45Mg and Al-19Si-0.45Mg alloy for the study examples, and make them be subjected to the hot extrusion deformation. For the hot-deformation Al-16Si-0.45Mg alloy, the aging treatment is performed in different temperatures with different holding times after540℃×(1.5,5,10h) solution treatment. Then we take the samples to do the friction and wear performance test under the load of300g and at the speed of2500r/min. Primary discussions have been done about the impact on the microstructures, the mechanical properties, the dry friction and wear behavior of the Al-16Si-0.45Mg hypereutectic alloy in different heat treatment conditions. We can draw conclusions as follows:1. The microstructure of the Al-16Si alloy which is achieved by the semi-continuous casting contains the primary silicon particles, the α-Al dendrites, and the α+Si eutectic structures. The microstructure of the Al-16Si-0.45Mg and Al-19Si-0.45Mg alloy contains the primary silicon particles, the α-Al dendrites, the a+Si eutectic structures and the black Mg2Si phase.2. The Si phase in the microstructures of hypereutectic Al-Si alloy which has gone the hot extrusion evolved into tiny particles distributed in Al matrix. The roundness of silicon phase particles of Al-16Si-0.45Mg alloy has been greatly improved after T6treatment. And the silicon particles grew up with the extension of solution holding time. 3. Compared with Al-16Si alloy, the mechanical property of Al-16Si-0.45Mg and Al-19Si-0.45Mg alloy is improved. The yield strength and tensile strength of Al-16Si-0.45Mg alloy after540℃×1.5h solution and180℃×3h aging treatment achieved270MPa and320MPa respectively, which increased by107.69%and77.78%respectively compared with extrusion state.4. The friction coefficient of Al-16Si, Al-16Si-0.45Mg and Al-19Si-0.45Mg alloy after hot extrusion is0.2494%0.2144and0.1643respectively. Adding Mg element is beneficial to strengthen the property and wear resistance of the alloy. And with the increase of silicon content in the alloy, the wear resistance has been improved.5. The friction coefficient of Al-16Si-0.45Mg alloy after T6treatment reduced from0.2144to0.1908, and reduced by12.37%. The size of Si particles grew up with the extension of solution holding time, which increased the role of supporting load of Si particle. Thus the wear resistance is improved and the friction coefficient is decreased. In the same aging condition, the friction coefficients of the alloy by5h and10h solution are lower than the alloy by1.5h solution.6. The wear mechanism of hypereutectic Al-Si alloy is the superposition effect of both the micro-cutting and the micro-breakout wear. The wear surface morphology contains the sliding furrows parallel to the direction and the peeling pits. The analysis of wear mechanism indicates that the main wear mechanism is abrasive wear, and the source of abrasive particles is mainly the peeling of crushing Si phase. At the same time it accompanied by oxidation and adhesion.