Microstructure and tensile properties of dissimilar metal gas tungsten arc welding of aluminium to titanium alloy

Abstract

Commercially pure aluminium and titanium alloy Ti–6Al–4V were welded by gas tungsten arc welding (GTAW) process using AA 4047 Al–Si filler material. The chemical composition of reaction layer at the interface of titanium alloy and weld zone was determined by electron probe microanalyser (EPMA) showing that continuous layer of intermetallic compound of TiAl base phase was formed and aluminium is partly replaced by silicon. Transmission electron microscopic examination confirmed formation of (AlSi)₃Ti intermetallic compound formed at the interface of Ti alloy and weld. In the weld zone, intermetallic phases containing Fe and Si were identified by EPMA analysis. These intermetallics were confirmed by X-ray diffraction technique. No intermetallic compound was found at the interface of weld and aluminium. Optical microscopy, scanning electron microscopy, microhardness, and tensile testing of the joints were used to characterise the resulting joints. The transverse strength of the weld joint is higher than that of the aluminium.