Electrochemical behavior of A356 Al alloy and its vortex and squeeze composites containing ZrO2 in 3.5 % NaCl solution

Corrosion of A356 Al alloy and its composites reinforced by ZrO2 and prepared by vortex and squeeze casting was studied in 3.5 % NaCl solution using poteniodynamic polarization and electrochemical impedance spectroscopy (EIS) techniques. The results of polarization and EIS indicated that the corrosion resistance of the vortex cast composites increases with the increasing in the vol. % of ZrO2 up to 20 % then decreases again at 30 % in the chloride solution. Also, the corrosion resistance of the squeeze cast composites increases as the squeeze pressure increases due to decreasing the porosity within these composites. Additional, the SEM micrographs well-showed that the defects and notches which appeared on the surface of the mechanically polished vortex cast composite were diminished due to growth of a protective passive film on the composite in the chloride solution. Also, the squeeze cast composite is covered by a thick passive film and less exposure to corrosion in comparing with surface of the vortex cast composite. Energy dispersive spectroscopy (EDS) spectra found out the presence of a passive aluminium oxide layer on the A356 Al alloy/ZrO2 composites.

High-Copper Cast Irons for the Products of Tribotechnical Applied

The paper presents the results of the development of a special group of cast composite materials based on nodular cast irons. The alloys were based on alloying cast iron with copper in amounts that exceed its solubility in liquid Fe-C-Si systems (Cu>6 wt.%). A new component is obtained in the structure of castings in the form of a complex mixture based on the Cu-phase. Inclusions are relatively large (up to 200 μm) and globular in shape, with a uniform allocation in the volume of the castings. This favorably distinguishes the obtained alloys from the known cast irons and gives them high antifriction properties. With isothermal hardening, it is possible to obtain the lowest values of wear for structures of lower bainite. Developed cast composite materials are recommended to be used as tribotechnical materials working in conditions of poor lubrication and corrosion.