The Use of Mechanically Derived Powders for Additive Manufacturing: Flow and Function

Metal additive manufacturing (AM) provides the opportunity of “on demand” customizable fabrication to minimize supply chain constraints. However, powder availability could become a similar constraint, and creating affordable regional sources for low-embodied energy powders will be a crucial step in distributed manufacturing. Current gas or water atomization processes methods for form metal powders (which are then often remelted in powder bed fusion) adds significant energy budget to the process. First, atomized powders are regularly sorted so that only a portion of the powder produced reaches the AM user. Secondly, if the alloy already exists in solid form, the energy needed to melt to form the powder form is an energetically “hungry” step. A powder creation method using cold mechanically derived (CMD) of particulates can create a wide range of alloy compositions with approximately 90% less embodied energy than gas atomization (GA). CMD powder is often less spherical than GA powders, and thus the powder flow characteristics in common powder bed systems must be demonstrated. Our study has shown that the flowability of Al 7075 and Copper 14500 powders made via GA and MF are similar at rates appropriate for powder bed additive methods. Particle morphology descriptions (size and shape) do not strongly correlate to tap density in this case, which suggests under common AM bed filling processes the bed density will be similar in both cases. Morphology comparisons and particle size/shape distributions were made by comparing large particle statistics, rather than solely comparing mean particle size. Laser powder bed fusion tensile specimens were formed from AL 7075 and heat treated to T6; the GA and CMD powders showed equivalent tensile test performance to both each other and conventionally wrought 7075.