Multistep modification of the surface of hypereutectic silumin by a pulsed electron beam of submillisecond duration: structure and properties

Abstract

We demonstrate the possibility of modifying hypereutectic silumin with the help of a pulsed electron beam of submillisecond duration characterized by a stepwise decrease in the energy density of the electron beam. It is shown that the selected modes of treatment make it possible to remelt the surface layer of the material down to a depth of 170 μm. It is demonstrated that the modification of hypereutectic silumin makes it possible to get a severalfold increase in the tribological and mechanical properties of the material, enhance the ultimate tensile strength and relative elongation as compared with the as-cast state, and lower the parameters of roughness down to R_a=0.07 μm and R_z=0.43 μm. It is established that the improvement of the mechanical and tribological properties of the alloy is explained by the formation of a multilayer submicrometer nanocrystalline structure characterized by the successive stepwise decrease in the energy density of the electron beam and the process of tempering of the surface layer formed as a result of multistep heat treatment.