Study of printability and porosity formation in laser powder bed fusion built hydride-dehydride (HDH) Ti-6Al-4V

Laser powder bed fusion (L-PBF) is a dominant process in the fast-emerging additive manufacturing (AM) industry. Despite the many advantages that can be gained by adopting AM, sustained future growth in this industrial sector requires AM to overcome several barriers, most notably, the formation of in-part defects and the high production cost. Motivated by the growing interest of reducing feedstock cost, we studied the cost-efficient hydride-dehydride (HDH) Ti-6Al-4 V powder in L-PBF and show that the in-part porosity can be controlled to produce nearly fully dense (> 99.8% density) components by optimizing process parameters. The process map that was developed with the HDH powder offers a general guideline for the usage of non-spherical powder in powder bed AM. In this work, we investigated the size, morphology, and spatial distribution of the powder-induced porosity in 3D and quantified the interaction between the HDH powder layer and keyhole fluctuation in-situ by utilizing advanced synchrotron-based x-ray computed tomography and dynamic x-ray radiography. With the assistance of a Monte Carlo image-based analysis, we propose two porosity formation mechanisms and attribute them to the unique characteristics of the HDH powder bed, i.e., variable local packing and larger particle size.