Title: Influence of diode laser surface melting on microstructure and corrosion resistance of 7075 aluminium alloy

Authors: A.C. Umamaheshwer Rao; V. Vasu; S.M. Shariff; K.V. Sai Srinadh

Addresses: National Institute of Technology, Warangal 506004, India ' National Institute of Technology, Warangal 506004, India ' International Advanced Research Centre for Powder Metallurgy and New Materials (ARCI), Hyderabad 500005, India ' National Institute of Technology, Warangal 506004, India

Abstract: High power diode laser (HPDL) has been used for surface melting of 7075-T651 aluminium alloy in order to induce changes in the microstructure and corrosion performance. Laser surface melting was carried out using 4 kW power with the scan rate of 10 mm/s in the nitrogen atmosphere. The microstructural study shown that within the resolidified laser-melted layer, most of the coarse constituent particles and the original grain boundaries of the wrought structure were removed. The grain boundaries of the resolidified structure were observed to be free from precipitates. The corrosion studies of the alloy were determined by potentiodynamic polarisation measurements and electrochemical impedance spectroscopy measurements in 3.5% sodium chloride solution. It was observed that the corrosion rate was reduced by four times, when compared with the untreated sample. The superior corrosion resistance was attributed due to absence of detrimental Al-Cu-Fe constituent particles from the surface of laser-melted layer.

Keywords: LSM; laser surface melting; high power diode lasers; microstructure; corrosion resistance; potentiodynamic polarisation; corrosion rate; EIS; electrochemical impedance spectroscopy; aluminium alloys.

DOI: 10.1504/IJMMP.2016.078055

International Journal of Microstructure and Materials Properties, 2016 Vol.11 No.1/2, pp.85 - 104

Received: 20 Jul 2015
Accepted: 28 Jan 2016
Published online: 31 Jul 2016 *

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