Effects of rapid multiple surface remelting by laser on the mechanical properties of Al – Si series aluminum alloys with different alloying elements such as Cu, Ni, Fe have been investigated to get fine microstructures and improve the mechanical properties of remelted zone using a rotating optical device. The thermal cycles during the rapid multiple remelting were recorded near the fusion line to determine the heating– and cooling rates during rapid multiple surface remelting. The heating rate was 1.37 × 104 °C and cooling rate 8.0 × 103 °C at travel speed of 1.67mm/s and rotating speed of 1200 rpm. These rates are quite high comparing with those in arc welding.
The microstructures of remelted zone showed the refining of dendritic arm from about 200 μ m of as–casted alloy to 2 or 3 μ m by the rapid multiple remelting. The Vickers hardness of the remelted zone increased depending on the content of alloying element such as Cu, Ni and Fe. The fatigue strengths of laser remelted specimens on topsurface were lower than those of as casted specimens, because of tensile residual stress in the remelted zone on top surface. The wear resistance of laser remelted surface was higher than that of as–casted specimens at higher slip rate in Ohgoshi type wear test. It is concluded that rapid multiple remelting of aluminum alloy by laser is available to improve the homogeneity of microstructures and mechanical properties such as wear resistance.