CORROSION BEHAVIOR OF LASER SURFACE MELTED 2014 ALUMINIUM ALLOY IN T6 AND T451 TEMPERS

It is generally accepted that laser surface melting (LSM) can be used for improving the localised corrosion resistance of various metallic alloys as a result of homogenisation and refinement of microstructures, and phase transformations. However, there are exceptions. For example, no improvement of pitting corrosion resistance of a wide range of aluminium alloys by LSM has been reported. This paper investigates the corrosion performance of laser-melted Al 2014 alloy in the T6 and T451 conditions to determine the key factors influencing pitting corrosion performance. LSM was carried out using a 3 kW CW Nd:YAG laser with a line beam profile. Examination of laser-melted surfaces in terms of microstructure, elemental distribution and phase analysis was performed using SEM/EDX, EPMA and XRD. Pitting corrosion resistance was evaluated using potentiodynamic anodic polarisation in de-aerated 1 M NaCl solution. Laser treatment enhanced the pitting potential by up to 170 and 110 mV for the T6 and T451 conditions respectively. The major factor contributing to the improvement appeared to be alloying elements, mainly of copper, in the aluminium matrix with refinement of the microstructure, with finer intermetallic particles, appear to playing a lesser role.