Effects of thermal undercooling and thermal cycles on the grain and microstructure evolution of TC17 titanium alloy repaired by wire arc additive manufacturing

Wire arc additive manufacturing (WAAM) can be used to repair blades or blisk made of titanium alloy with the advantage of high efficiency and low-cost. In this work, the finite element model of repairing the blade based on the arc heat source was established to investigate it. Results showed that the maximum effect of thermal undercooling appeared when the peak current transformed to the base current (1 Hz or 5 Hz), which will promote the grains refinement with the combination of sufficient constitutional supercooling. Compared to the single-layer deposition, the microstructure in the near-heat affected zone (near-HAZ) of multi-layer deposition changes from the metastable beta phases to the extremely fine alpha phases, which was caused by the repeated thermal cycles.

Automated summary

Wire arc additive manufacturing (WAAM) is an efficient and cost-effective method for repairing blades or blisks made of titanium alloy. In this study, a finite element model based on the arc heat source was established to investigate the repair process. The results showed that the maximum effect of thermal undercooling occurred when the peak current transformed into the base current, leading to grain refinement. Compared to single-layer deposition, the microstructure in the near-heat affected zone (near-HAZ) of multi-layer deposition changed from metastable beta phases to extremely fine alpha phases due to repeated thermal cycles.