Optimization of laser powder bed fusion process to enhance mechanical properties of as-built Ti–6Al–4V samples

Abstract

To date, as-built Ti-6Al-4V samples with high tensile strength and elongation sufficient to meet the ASTM B348 standard have been considered unattainable in additive manufacturing due to inherent defects, such as rough surface and internal porosity, associated with powder-based processes. However, this study demonstrates for the first time that Ti-6Al-4V structures, even in their as-built state, can achieve mechanical properties that satisfy the ASTM B348 standard through proper optimization of the laser powder bed fusion process (PBF-LB/M). The effects of process conditions on relative density, part precision, surface roughness, microstructure, and mechanical properties were systematically analyzed. The key parameters for the optimization were found to be the volumetric energy density and hatch distance. The optimal process condition, characterized by an energy density of 67 J/mm 3 and a hatch distance of 60 μ m, yielded a relative density of 99.9%, part precision of 99.9%, and a side surface roughness of 26.7 μ m. The corresponding mechanical properties were an ultimate tensile strength of 1214 MPa and an elongation of 11.7% in the longitudinal direction, whereas they were 1173 MPa and 11.1% in the transverse direction, respectively. This study demonstrates the importance of meticulous process control, particularly in terms of energy density and hatch distance, in PBF-LB/M and offers a pathway for enhancing the mechanical properties of as-built Ti-6Al-4V components. • As-built Ti-6Al-4V built by powder bed fusion meets ASTM B348 • Hatch distance, as well as energy density, is critical in mechanical properties • Mechanical properties are maximized when surfaces are smooth • Maximum UTS of 1241 MPa and 11.7% elongation attained in the as-built state

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