High-temperature strength and microstructural evolution of Ti-6Al-4V alloy fabricated by wire Arc additive manufacturing under elevated temperature

Abstract

This study investigates the high-temperature mechanical properties and compressive deformation behavior of Ti-6Al-4V fabricated by Wire Arc Additive Manufactured (WAAM), in comparison with its hot-rolled counterpart. The WAAM alloy exhibited a fine α-lath Widmanstätten structure containing a nano-film β phase, which developed through solid-state β→α transformation during cooling under a steep thermal gradient induced by rapid solidification and interpass thermal cycling. In contrast, the wrought alloy showed a bimodal microstructure with coarse equiaxed α and α + β lamellar colonies. Compression tests at RT, 300 °C, 500 °C, and 700 °C revealed that WAAM alloy retained higher yield strengths across all temperatures (RT: 1034.1 MPa, 300 °C: 845.7 MPa, 500 °C: 646.2 MPa, 700 °C: 320.4 MPa). This was attributed to the fine α-lath structure, high angle grain boundary (HAGB) fraction, and α/β interface strengthening. However, at 700 °C, accelerated kinking and α-lath fragmentation led to localized dynamic recrystallization (DRX) and rapid flow softening. These findings demonstrate the thermal stability and deformation resistance of WAAM alloy. Based on the above results, the microstructural control approach to enhance its high-temperature performance was also discussed.