Formation of Structure and Properties of Silumin on Electron-Beam Processing

The analysis of the gradient structure-phase states and nanohardness of hypoeutectoid silumin at 120 mu m depth after the processing by high intensive electron beams in the regime of top layer melting has been carried out. It has been shown that depending on the depth to the surface of irradiation the electron beam processing leads to the dissolution of the primary inclusions of silicon and intermetallides and the formation of structure of high-speed cellular crystallization of aluminium and the grains of plastic eutectic. A 1.5-2 fold decrease in the concentration of the alloying elements has been detected. The hardness of irradiated silumin changes in a nonmonotonous way and reaches the maximum values exceeding the hardness of the initial state by 3.8-4.2 times in the layer located at 30-50 mu m depth. The interpretation of the observed changes in structure and hardness on irradiation has been given.