Alloying of aluminium surface with Q-switched Nd:YAG laser

Abstract

In surface modification, laser has been used as a tool to improve and enhance the surface properties of metallic alloys through laser alloying technique. Therefore, the aim of this study is to modify aluminium surface with iron (Fe) and copper (Cu) by Q-switched Nd:YAG laser. The Q-switched Nd:YAG laser is operating at a fundamental wavelength of 1064 nm with 10 ns pulse duration. The laser optimized parameters in this work are focus distance, pulse width and pulse energy. The target consists of a pure aluminium plate and the two alloying elements used are iron (Fe) and copper (Cu) powders. The alloying elements were well mixed and prepared in four different ratios (Fe:Cu) of (1:0), (1:1), (2:1), and (3:1). The surface alloying process was carried out by varying the laser output energy delivered to the targets from 67 to 331 mJ per pulse. The modified surfaces were characterized by using three types of analysis; structural elemental, and mechanical analysis. The results from field emission scanning electron microscopy (FESEM) showed that the surface microstructures change significantly compared to the untreated surface. The formation of alloyed layer due to the rapid melting and solidification processes of alloying elements with aluminium substrate was observed. In addition, all the treated surfaces show less porosity and are free from any cracks. X-ray diffraction (XRD) analysis of the treated surface showed the formation of new compounds which comprise AlCu, AlFe, CuFe and AlFeCu. The maximum hardness of the treated surfaces as measured using microhardness tester is 86.2 HV which is two times higher than that of the untreated surface. The formation of intermetallic phases and the change in the surface microstructures are responsible for the increase in the surface hardness compared to untreated one.