Laser deposition of (Cu + Mo) alloying reinforcements on AA1200 substrate for corrosion improvement

Abstract

Poor corrosion performance of aluminium alloys in marine environment has been a subject of intensive research recently. Aluminium substrate was alloyed with a combination of two metallic powders (Cu + Mo) using an Nd: YAG solid state laser. Solidification of the laser induced melt pool led to the precipitation of different intermetallic compounds. Characterisation of the resultant microstructure was carried out by optical and scanning electron microscopes. X-ray diffraction and energy dispersive spectrometry was used for phase and elemental composition analyses respectively. Experimental results showed that the microstructure of the alloyed zone consisted of a continuous network of Al2Cu precipitates which is the initial phase at the background enveloping the Al-matrix, on top of the initial phase are the Al5Mo intermetallic precipitates and eutectics of (a-Al + Al2Cu) and (a-Al + Al5Mo). The addition of 50%Cu and 50%Mo to the Al solid solution increased the electrode potential; decreased the anodic activation; promoted the formation of stable passivation on the surface of aluminium and greatly deceased corrosion reactions. A significant increase in the corrosion resistance of the aluminium was achieved as a result of laser surface alloying