Intergranular corrosion susceptibility of friction stir processed aluminium alloy 5083

Abstract

The amalgamation of high strength and low density of aluminium alloys makes it suitable for light weight structural applications. Aluminium alloy AA5083 is prone to intergranular corrosion, when exposed to aggressive chloride containing marine environments. When aluminium alloy 5083 is exposed to marine environments, the continuous network of secondary phase particles present in the matrix reacts with the chloride ions and dissolves into the solution, creating new cites for corrosion. In addition to this phenomenon, secondary phase particles form galvanic couple with primary phase of the matrix, accelerating the corrosion. With an objective to improve the intergranular corrosion resistance, AA5083 was subjected to friction stir processing (FSP). FSP trials were conducted by varying the tool rotation speed, tool traverse speed and tool shoulder diameter, as per face centered central composite design. The intergranular corrosion susceptibility of friction stir processed AA5083 was studied by nitric acid mass loss test according to the ASTM G67-04 standard. Mathematical model was generated using linear – radial basis function and the model was used to study the effect of process parameters on the intergranular corrosion susceptibility of friction stir processed AA5083. The results indicate that FSP results in refinement of grain structure, dispersion and partial dissolution of secondary phase particles in the matrix, thereby reducing the intergranular corrosion susceptibility of AA5083.