Post welding heat treatment improving mechanical properties on Ti-6Al-4V

Abstract

Ti-6Al-4V can be easily welded by tungsten inert gas (TIG) welding process. However, the parent material properties tend to worsen because of microstructural changes and residual stresses. Post welding heat treatments (PWHT) are used to restore the mechanical properties of the joints. In this work, automotive components made out of Ti-6Al-4V are welded by TIG process. Although the as-welded joints showed e reasonable static strength, the strain at failure resulted quite low so that a toughness improvement via post welding heat treatment was required. This contribution summarizes the preliminary results obtained by PWHT on both butt- and overlap-welded joints made out of titanium alloy (grade 5). Different heat treatment (HT) recipes were tested and results were showed in terms of stress-strains curves as well as microstructure and microhardness profiles. It is found that, with reference to overlap joints, a stress-relieving HT optimizes both the mechanical properties and toughness. A partial solution HT followed by ageing is required to increase significantly the static strength of butt-welded joints, unfortunately without toughness improvement.