Study on the Forming Process and Microstructural Formation Mechanism of Wire and Arc Additive Manufacturing Ti‐6.5Al‐3.5Mo‐1.5Zr‐0.3Si Titanium Alloy

Ti‐6.5Al‐3.5Mo‐1.5Zr‐0.3Si titanium alloy was produced using tungsten inert gas wire and arc additive manufacture (WAAM) technology. The study investigated the impact of WAAM process parameters and their interactions on weld bead size and microstructure. The columnar‐equiaxed transformation model was utilized to analyze the solidification process of the titanium alloy weld pool. The findings revealed that bead width increases with higher welding current and decreases with increased welding speed. Conversely, bead height decreases with higher welding current and speed but increases with increased wire feeding speed. Notably, welding current and speed, as well as welding current and wire feeding speed, exhibited significant interactions on bead width and height. The optimized process parameters for arc additive manufacturing of titanium alloy were determined as follows: wire feeding speed of 149 cm/min, welding speed of 25.2 cm/min, and welding current of 140 A. During the weld solidification process, the temperature gradient decreased from bottom to top, while the solidification speed increased in the same direction. Furthermore, an increase in welding current and a decrease in welding speed shifted the solidification conditions towards the columnar crystal region, thereby promoting the growth and formation of columnar crystals.