In this study, the embrittlement behavior of as-built Ti–6Al–4V manufactured by Laser Powder Bed Fusion (PBF-LB/M) was investigated with a focus on effects caused by in-process heat accumulation. The microstructural evolution was analyzed through systematic heat treatment of Ti–6Al–4V samples, Vickers hardness testing, and differential scanning calorimetry (DSC) analysis. A distinct hardness peak was observed at around 500 \(\mathrm {^\circ C}\) , coinciding with an irreversible exothermic event seen in DSC measurements, suggesting a distinctive transformation specific to the \(\alpha ^{\prime }\) microstructure. Tensile tests on embrittled samples showed an increased yield strength ( \(1197\, \pm \, 34\) MPa) and an ultimate tensile strength ( \(1252\, \pm \, 19\) MPa) but a significantly reduced ductility ( \(0.7\, \pm \, 0.6\) % elongation). Compression testing confirmed high strength and low ductility, while Charpy impact energy dropped by 45.9 % compared to the as-built condition. Fractographic analysis indicated a transition to mixed trans- and intercrystalline fracture modes. Although direct evidence of \(\mathrm {Ti_{3}Al}\) precipitation remains inconclusive, the literature suggests that vanadium segregation and \(\beta\) phase stabilization could provide favorable conditions for its formation. These results highlight the critical impact of local reheating on mechanical performance and emphasize the need to consider embrittlement phenomena in process parameter optimization and the design of support structures. The study contributes to a fundamental understanding of microstructural sensitivity in PBF-LB/M Ti–6Al–4V and supports the development of more robust and certifiable additive manufacturing strategies.
