EFFECT OF SEVERE PLASTIC DEFORMATION AND OXIDATION ON THE STRUCTURE AND MICROHARDNESS OF THE SILUMIN SURFACE LAYER
Structural changes occurring in the surface layer, up to 10 μm thick, of silumin (Al-17 % Si alloy) in the case of deformation under sliding friction and subsequent oxidation at 100 and 200 °C for 1 hour are studied by metallographic analysis, X-ray diffraction analysis and electron microscopy. Frictional deformation was carried out in air at room temperature and in liquid nitrogen (at -196 °C). Deformation under these conditions is shown to form a nanocrystalline structure in the surface layer of the Al-17 % Si alloy and to increase its microhardness by a factor of 1.8. In the alloy surface under friction, severe plastic deformation, as well as the high affinity of oxygen to aluminum and silicon, initiates the appearance of anomalously supersaturated solid solutions of oxygen in aluminum and silicon. Oxidation of the deformed Al-17 % Si alloy at 100 °C for 1 hour increases its microhardness as a result of the decomposition of anomalously supersaturated solid solutions of oxygen in aluminum and silicon and the formation of their oxides.