Influence of post-heat treatment with super β transus temperature on the tensile behaviour of LPBF processed Ti6Al4V

Abstract

This paper investigates the tensile behaviour of Laser powder bed fusion (LPBF) processed Ti6Al4 V samples under three build orientations. The effect of microstructural changes from the post-heat treatments (PHTs – 850 °C, 950 °C 1050 °C) was assessed. The microstructural characterization was performed using optical microscopy, X-ray diffraction, and SEM techniques. The tensile tests were performed using a uniaxial universal testing machine (UTM). The fractal dimension analysis was performed on the fractured surfaces using ImageJ software integrated with an open-source MultiFrac plug-in. The PHT at a higher temperature (i.e., 1050 °C) induces a higher amount of β phase than the other PHTs. The PHT performed at 1050 °C exhibited α-Widmanstatten microstructure consisting of elongated β and a small amount of α. The PHT induces an isotropic behaviour in the LPBF-processed samples. However, the ductility of specimens subjected to PHT at 1050 °C showed ∼ 67%, 40%, and 177% improvement under horizontal (0°), inclined (45°), and vertical (90°) orientations than as-printed samples. Further fractal dimension analysis corroborates well with the ductility values of PHT samples. Therefore, the combination of fractography analysis and fractal dimension approach can be a promising methodology towards fractured surface characterization of additively manufactured metal parts.