Electrochemical and surface studies of 0.95 Mg-Al-alloy and pure copper joints prepared using friction stir welding with low-medium-high tool travel speeds

Abstract

Friction stir welding (FSW) is a technique currently used by weldment industries. In this study, FSW was used to join two dissimilar metals, copper and 0.95 Mg-Al-alloy. The process parameters and tool travelling speed were determined for a defect-free weldment. The corrosion resistance of the joint was studied with electrochemical methods in 3.5 wt.% NaCl solution. A scanning Kelvin probe was used to detect localized changes at the metal and weldment surface. Samples were characterized to explore the metallurgical effects and the effect of process parameters on the microstructure during the welding deformation process. The primary α-Al phase formed during solidification can significantly limit the growth of the Cu9Al4 phase as observed by optical microscopy. With the increase in tool travel speed, α-Al precipitates in the CuAl matrix created during welding became coarser. The electrochemical results illustrate that the tool travelling speed of 40 mm/min produced the greatest corrosion resistant property.