Narrow-gap tungsten inert gas welding of 78-mm-thick Ti–6Al–4V alloy

Abstract

Narrow-gap tungsten inert gas welding with in situ protective system is applied to 78-mm-thick Ti–6Al–4V alloy. The martensite basketweave microstructure is formed in fusion zone (FZ), and heat-affected zone (HAZ) near FZ consists of acicular martensite and a small portion of primary alpha phase. The HAZ near base metal (BM) consists of primary alpha and transformed beta phase. Microhardness values of FZ and HAZ are relatively higher, and peak values appear at HAZ near FZ. The mechanical heterogeneity is dependent on variation of beta phase and martensite, which in turn depend on specific thermal cycle(s). The average tensile strength reaches 783.3 MPa and is 91.2% of BM, which appears in the middle of the weld with orthogonal martensites.

A Laser-Induced TIG Arc Narrow-Gap Welding Technique for TC4 Titanium Alloy Thick Plates Based on the Spatial Position Control of Laser, Arc and Filler Wire

“…This method significantly reduces the cross-sectional area of the weld and the amount of weld metal required, resulting in more efficient production with lower energy consumption and reduced costs, which is the development trend of large-size thick plate welding [10,11]. Laser welding and tungsten inert gas welding (TIG) are commonly used for narrow-gap welding of titanium alloy plates [12]. However, the heat source of traditional TIG welding is prone to fluctuations, which can result in arcing on the sidewall and unstable layer height during narrow-gap welding.…”