Corrosion behaviour of Al 7075 /TiC composites processed through friction stir processing

Abstract

Aluminum alloys are promising for structural applications due to their high strength-to-weight ratio, resistance to corrosion and light weight. Aluminum/aluminum alloy matrix composites reinforced with particles like ceramic possess higher strength and hardness. Aluminum alloy 7075-T651 of 6.35 mm thick plate was used as a base material for the present study and surface modification was done using friction stir processing (FSP). H13 tool steel in the heat-treated condition was used as the tool material. TiC particle of 3.5µm size was used as a reinforcement in different volume fractions 2, 4 and 6 vol.% respectively. FSP process was carried out at travel speed of 30 mm/min and a rotational speed of 1200 rpm. Corrosion studies were carried out using 3.5% NaCl with varying the molarity of the electrolyte (1M, 2M, and 3M NaCl). Corrosion rates were calculated from corrosion current density (Icorr), by using polarization techniques with the help of Tafel extrapolation. The effect of TiC on microstructural development, hardness and corrosion behaviour was studied. It was observed that the corrosion resistance of the Al 7075-TiC composite was higher than the Al 7075-T651. The corroded surface morphology of revealed pits on the surface and the number of pits increased with increasing the concentration of NaCl..