The
microstructures and
wear resistance of Al 20%Si and Al 30%(Mass fraction)Si alloys solidified under different
cooling rate have been researched. Results of experiments indicates that effects of the cooling rate on solidification microstructures and wear resistance of
alloy are significant. When cooling rate increases, the phase constitution of
solidification microstructure and the shape and sizes of primary silicon crystal in the microstructure of Al 20%Si and Al 30%Si alloys change obviously. The
solidification microstructures both of the specimen solidified in furnace of which the
Cooling rate is less than 0.1?K/s and the specimen solidified in refractory mold of which the cooling rate is less than 1?K/s are composed of ( α +Si) eutectic and primary Si crystal, and the coarse plate shaped primary Si crystal and needle shaped eutectic Si crystal are inspected in the solidification microstructure. The solidification microstructures of the specimen solidified in metal mold of which the cooling rate is about 10?K/s is composed of ( α +Si) eutectic and primary Si crystal and the dendritic α phase, and the shape of primary Si crystal is plate or block, the eutectic Si crystal is also needle shaped, the dendritic α phase emerged in the metal mold casting specimen. The solidification microstructures of the over spray powder cooled by (10 4～10 6)K/s is also composed of ( α +Si) eutectic and primary Si crystal and the dendritic α phase, and the shape of most of primary Si crystals are fine block. The solidification microstructures both of spray formed Al 20%Si alloy and Al 30%Si alloy are composed of Si crystal and α phase, the fine Si crystals are well distributed in the α phase matrix. With increasing cooling rate, the size of silicon crystal diminished, the wear resistance of Al 20%Si alloy and Al 30%Si alloy increases significantly due to the wear mechanism of alloy changed.