Laser surface melting of aluminium alloy 6013 for improving pitting corrosion fatigue resistance

Laser surface melting, using an excimer laser, was employed to improve the resistance to fatigue cracking of aluminium alloy 6013 induced by pitting corrosion. Analysis of the electrochemical impedance measurements showed that the laser-formed AlN and/or Al2O3 layer can greatly reduce the rate of electrochemical reaction.The results of the corrosion fatigue tests showed that the total fatigue life of the alloy increased noticeably after the laser surface treatment. The improvement is considered to be due to the excellent initiation resistance to the pitting corrosion of the laser-treated specimens, especially the N2-treated specimens. However, a higher overall fatigue crack propagation rate may well be experienced by the laser-treated specimens. This could be explained by the difference in the critical crack length for the fast crack growth of the untreated and laser-treated specimens.