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INTRODUCTION

LIQUID-PHASE surface treatment by means of laser, electron beam, and other heat sources has widely been examined and applied on aluminum alloys.[1–4] It has been reported that surface alloying of aluminum with transition metals (TM) like nickel, chromium, tungsten, molybdenum, and iron resulted in the formation of AlxTMy intermetallics, along with structural modification, and thereby, improved surface properties like hardness, corrosion, and wear resistance. Heydarzadeh Sohi[5] investigated electron beam surface alloying of LM13 aluminum with nickel. The results showed a significant increase in hardness and wear life of LM13 aluminum alloy owing to the formation of hard Al3Ni intermetallic phase. Ansari et al.[6] investigated pulsed Nd:YAG laser surface alloying of AA6061 aluminum with chromium and showed this treatment resulted in the formation of Al7Cr and Al4Cr intermetallic phases on the surface of AA6061 aluminum, and as a result, an improvement in surface hardness was obtained. Rajamure et al.[7] studied the corrosion resistance of laser surface alloyed AA1100 aluminum with tungsten and reported a substantial improvement in corrosion resistance of AA1100 aluminum due to the formation of Al4W intermetallic phase. In another study, Rajamure et al.[8] investigated wear behavior of laser surface alloyed MOHAMMAD ANSARI, Research Assistant, REZA SOLTANI, Assistant Professor, and MAHMOUD HEYDARZADEH SOHI, Professor, are with the School of Metallurgy and Materials Engineering, College of Engineering, University of Tehran, P.O. Box 111554563, Tehran, Iran. Contact e-mail: [email protected] ZIA VALEFI, Assistant Professor, is with Malek-Ashtar University of Technology, Tehran, Iran. Manuscript submitted June 22, 2015. Article published online January 12, 2016 1698—VOLUME 47A, APRIL 2016

AA1100 aluminum with molybdenum and reported enhancement in wear resistance due to the formation of Al8Mo3 and Al5Mo intermetallic phases. Liquid-phase surface alloying of aluminum with iron using laser beam has been reported in a couple of articles. Gjønnes and Olsen[9] investigated the effects of two different CO2 laser beam settings on hardness and microstructure of surface alloyed 5000-aluminum alloy with iron and reported an improvement in hardness owing to the formation of Al3Fe intermetallic phase. In another study, Tomida and Nakata[10] reported enhanced surface hardness and wear resistance of Fe-Al composite layer on AA5052 aluminum plate through application of CO2 laser surface alloying. In these researches, laser surface alloying of aluminum was carried out using continuous wave CO2 lasers. Metallic materials reflect a major portion of the laser energy (reflectivity  1 for far infrared at k = 10 lm). CO2 laser with its long wavelength (10.6 lm) suffers from poor absorption during materials’ interaction, especially for aluminum, which has high reflectivity. It is, therefore, advised to use laser beams with short wavelength for liquid-phase surface treatment of metals, particularly for the case of aluminum base materia