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The present work exploits the customized heat treatment (CHT) to study the porosity levels of Optical microscopy evaluates the porosity level and microstructure in different conditions. Further, the porosities are classified as inter-micropores (size < 10 µm) and super-micropores (size > 10 µm). Moreover, the XRD technique was used to analyse the different phases that arose during laser powder bed fusion (LPBF) and CHT. The CHT at elevated temperature (1050ºC) helps to reduce the overall porosity level by two times that of as-printed samples due to the sintering self-healing phenomenon. Interestingly, the super-micropores observed in as-printed samples are reduced via CHT, which is favourable for enhancing mechanical properties. Moreover, the refinement of microstructures into different phases after CHT has improved the densification behaviour. (i). Classification and quantifications of the porosities level of LPBF processed Ti6Al4V alloy under both directions due to CHT. (ii). The effect of CHT and its pore self-healing mechanism and microstructure refinement on LPBF processed Ti6Al4V alloy. (iii) This study reveals that the CHT technique can be beneficial in introducing isotropic microstructure and densifying the distinctive LPBF components.

The present work exploits the customized heat treatment, and laser powder bed fusion process to build direction effects on the densification behaviour and microstructural development in Ti6Al4V alloy. Optical microscopy evaluates the porosity and microstructure in different conditions. Further, the porosities are classified as inter-micropores (size < 10 µm) and super-micropores (size > 10 µm). Classification and quantifications of the porosities of laser powder bed fusion processed Ti6Al4V alloy under both directions due to customized heat treatment. The effect of customized heat treatment, the corresponding pore self-healing mechanism, and microstructure refinement on laser powder bed fusion-processed Ti6Al4V alloy were discussed. Moreover, the X-ray diffraction technique was used to analyse the different phases during laser powder bed fusion and customized heat treatment. The elevated customized heat treatment helps to reduce the overall porosity by two times that of as-printed samples due to the sintering self-healing phenomenon. Interestingly, the super micropores observed in as-printed samples are reduced via customized heat treatment ∼ 44% in a horizontal direction and ∼ 46% in a vertical direction, respectively, which is favourable for enhancing mechanical properties. This is because reducing these micropores leads to improved ductility. The ductility of the customized heat treatment executed sample was ∼ 68% in a horizontal orientation and ∼180% in a vertical orientation. The isotropic index for ductility in as-printed Ti6Al4V in the horizontal and vertical directions is 0.61. In contrast, it is 0.97 for customized heat treatment in both orientations showing high isotropy for customized heat treatment samples compared to as-printed samples. This study reveals that the customized heat treatment technique can be beneficial in introducing isotropic microstructure and densifying the distinctive laser powder bed fusion components.

In this study, thin tubes are mimicked based on the architecture of Euplectella aspergillum and studied for fatigue performance under variable amplitude loading. The thin tubes are fabricated with Ti-6Al-4V material using the selective laser melting (SLM) process. SLM printed components are always subjected to residual stresses, which can reduce fatigue performance of the components. Heat treatment effect on the fatigue performance, microstructure, and residual stress is studied. Complex geometry and sharp corners in the bioinspired tubes result in stress concentration, which further reduces the fatigue performance. The value of residual stresses at the sharp corners is dependent on the height of the tube, thickness of struts, and intersection of different struts. Heat treatment significantly reduces the residual stresses and increases the fatigue life of the thin tubes; however, strength decreases after heat treatment. Heat-treated thin tubes showed a higher concentration of (α + β) phase, which results in decreased residual stress and improved ductility of the thin tubes. Advanced bionic thin tubes can be used for lightweight crash boxes, sandwich panels, bio-implants, grid stiffened structures, etc.