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

초록

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 alpha-lath Widmanst & auml;tten structure containing a nano-film beta phase, which developed through solid-state beta ->alpha 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 alpha and alpha + beta lamellar colonies. Compression tests at RT, 300 degrees C, 500 degrees C, and 700 degrees C revealed that WAAM alloy retained higher yield strengths across all temperatures (RT: 1034.1 MPa, 300 degrees C: 845.7 MPa, 500 degrees C: 646.2 MPa, 700 degrees C: 320.4 MPa). This was attributed to the fine alpha-lath structure, high angle grain boundary (HAGB) fraction, and alpha/beta interface strengthening. However, at 700 degrees C, accelerated kinking and alpha-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.

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