Characterization of the microstructure and mechanical properties of Ti-6Al-4V alloy fabricated by wire-arc additive Manufacturing: Insights into fracture behavior and strengthening mechanism

초록

The microstructure and mechanical properties of Ti-6Al-4V alloy fabricated using wire-arc additive manufacturing (WAAM) were investigated and compared with those of a conventional hot-rolled alloy (reference wrought material). The primary objective of this study was to clarify the relationship between the microstructure developed during the WAAM process and the resulting mechanical performance. Microstructural analysis revealed that the Widmansta<spacing diaeresis>tten morphology observed in the WAAM Ti-6Al-4V, which is characterized by fine alpha-lath structures and a low beta-phase fraction, was influenced by rapid cooling and layer-by-layer reheating. In contrast, the wrought Ti-6Al-4V displayed a more uniform and stable microstructure consisting of coarse equiaxed alpha grains and a higher beta-phase fraction. Tensile testing results showed that the WAAM Ti-6Al-4V demonstrated a higher ultimate tensile strength, whereas the wrought Ti-6Al-4V exhibited relatively higher elongation. The higher strength of the WAAM Ti-6Al-4V was mainly attributed to a stress concentration and limited slip transmission at alpha-lath boundaries, whereas the wrought Ti-6Al-4V exhibited a ductile fracture behavior, with void formation at alpha/beta interfaces due to its coarse equiaxed alpha grains and higher beta-phase fraction. This study systematically elucidated the correlation between the microstructure and mechanical properties of WAAM Ti6Al-4V and tried to provide valuable insights into the potential applications of WAAM Ti-6Al-4V.

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