Effect of heat input on microstructure and tensile properties of laser welded Ti–3Al–6Mo–2Fe–2Zr alloy joint

Abstract

The heat input during laser welding process has significant influence on microstructure and properties of the joints, whereas there is currently limited research concerning the influence of heat input during laser welding process of β titanium alloys. The microstructure and tensile properties of laser welded Ti–3Al–6Mo–2Fe–2Zr (wt.%) joints under different heat inputs were investigated in this paper. Numerical simulation process was used to explain the microstructure evolution in HAZ and fusion zone. The microstructure of HAZ is divided into three different regions from fusion line to base metal. In near-HAZ, mid-HAZ, and far-HAZ, the microstructures are composed of single β phase, β + αp, and β + αp + retained αs, respectively. In fusion zone, the microstructure consists of single β phase because of the fast cooling rate and high content of β stabilizing elements. The ultimate tensile strength (UTS) of laser welded specimens is lower than that of base metal due to the lack of strengthening phase and the coarsening of β grains. Higher heat input further exacerbates the coarsening of β grains in the fusion zone and HAZ, which consequently results in the decrement of UTS of the joints.

Keywords

• β titanium alloy
• Laser welding
• Heat input
• Microstructure
• Tensile properties