Gas Pore Formation in Powder Bed Fusion

Additive manufacturing (AM) of metal materials based on powder bed fusion technology is widely used now in many industries. A known limitation of this type of manufacturing is the formation of gas pores in bulk material arising from stochastic events related to molten metal fluid instabilities of a vapor depression. Here we present a combined X-ray imaging and infrared pyrometry study of pore formation in repeated adjacent tracks, and quantify the correlations of pore positions and sizes for a common material (Aluminum 6061) of interest in AM as a function of its laser processing conditions. We find in both cases that an existing pore in one track often catalyzes the formation of another pore in a consecutive track at the distance of closest approach. In a raster scan strategy commonly used to construct bulk material, this phenomenon has the result of forming perforations, or lines of pores transverse to the scanning direction in a rastered patch. If controlled, this effect can be eliminated to improve the yield strength of the build, or exploited to create programmable failures for specific purposes.



Distribution A. Approved for public release: distribution unlimited. (AFRL-2023-5001). Date Approved 10-10-2023.