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Increasing the productivity of laser powder bed fusion: Influence of the hull-bulk strategy on part quality, microstructure and mechanical performance of Ti-6Al-4V

Journal Contribution - Journal Article

To increase the productivity of Laser Powder Bed Fusion (LPBF), a hull-bulk strategy can be implemented. This approach consists in using a high layer thickness in the core of the part, hence reducing the build time, and a low layer thickness in the skin, to maintain a high accuracy and good surface finish. The present study investigated to what extent this strategy affected the surface roughness, relative density, microstructure and mechanical properties of Ti-6Al-4 V parts. Ti-6Al-4 V specimens were built using two distinct sets of process parameters, one optimized for a 90 μm-layer thickness in the bulk and the other for a 30 μm-layer thickness in the hull. In addition to surface roughness and relative density measurements, a thorough microstructure analysis was done using both optical microscopy and SEM. Additionally, EBSD measurements and numerical reconstruction of the parent β grains were performed to evaluate the mesostructure and texture evolution from hull to bulk. Microhardness measurements and tensile tests were done to assess the effect of the hull-bulk strategy on the mechanical properties. This analysis was completed on both as-built and stress-relieved specimens. The present study demonstrated the possibility of using the hull-bulk strategy to build high-quality Ti-6Al-4 V parts, without impacting their tensile properties, hence increasing the productivity of the process by a geometry-dependent factor, typically ranging between 25 % and 100 %.
Journal: Additive Manufacturing
ISSN: 2214-8604
Volume: 33
Number of pages: 10
Publication year:2020