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THE attractive mechanical properties of Mg and its alloys have prompted their increasing use in automobile and aerospace applications. However, their poor corrosion resistance has restricted their wider use. Alloy microstructure has a profound influence on the corrosion properties of any alloy system. Generally, the a-solid solutions of Mg alloys are anodic to the intermetallic particles and are preferentially corroded,[1–9] except in the case of Mg-8Li alloy,[10] where the intermetallic particles are more anodic than the a-solid solution. Suitable tailoring of the surface microstructure and/or chemistry is a common approach to improving the corrosion resistance of a susceptible metal/alloy. For this purpose, different rapid solidification processes have been employed for various Mg alloys.[11–30] In contrast to the conventional casting processes, rapid solidification processes generate a highly refined microstructure with a fine dispersion of intermetallic particles and produce a homogeneous distribution of alloying elements with extended solid solutions.[31] Among the various rapid solidification processes, laser surface modifications (melting/alloying/cladding) provide several advantages, such as delivery of conP. CHAKRABORTY BANERJEE, formerly Ph.D. Student with the CAST Cooperative Research Centre, Hawthorn, VIC 3122, Australia, and Department of Chemical Engineering, Monash University, Melbourne, VIC 3800, Australia, is now Post-doc Fellow with the Department of Mechanical and Aerospace Engineering, Monash University. R.K. SINGH RAMAN, Professor, is with the Department of Chemical Engineering, Monash University, and also with the Department of Mechanical and Aerospace Engineering, Monash University. Contact e-mail: [email protected] Y. DURANDET, Research Fellow, is with the Industrial Research Institute Swinburne (IRIS), Swinburne University of Technology, Hawthorn, VIC 3122, Australia. G. McADAM, Senior Research Scientist, is with the Defence Science and Technology Organisation, Fishermans Bend, VIC 3207, Australia. Manuscript submitted February 27, 2012. Article published online January 12, 2013 2346—VOLUME 44A, MAY 2013

trolled quantum of energy or power with a precise spatial distribution, short processing time, flexibility of operation, economy of material consumption, formation of a relatively narrow heat-affected zone, and precision of operation.[18,29] Laser surface treatments have been reported to improve the corrosion and pitting resistance of various alloy systems[18–26,32–37] as well as Mg alloys.[18–26] Majumdar et al.[18] reported an improvement in pitting resistance of MEZ alloy after laser surface melting and attributed this improvement to the combined effects of grain refinement, visible absence of reprecipitation of the cathodic intermetallic phases, and enrichment of alloying elements in the solid solution. Coy et al.,[19] Guan et al.,[20] and Gao et al.[21] have reported improvements in corrosion resistance of AZ91D alloy as a result of laser surface melting. However, Guan et al.[20] and