Precipitate Size in GRCop-42 and GRCop-84 Cu-Cr-Nb Alloy Gas Atomized Powder and L-PBF Additively Manufactured Material

Laser Powder Bed Fusion (L-PBF of Glenn Research Copper 42 or 84 (GRCop-42 or GRCop-84), a Cr2Nb precipitation-hardened high conductivity copper alloy, with tensile strength superior to other competing copper alloys. Precipitate diameters within GRCop-42 gas-atomized powder increased with powder diameter due to slower cooling rates, however unlike GRCop-84, no threshold diameter above which extensive precipitate agglomerations form was observed in GRCop-42. Large Cr2Nb crystals were observed in GRCop-42 powder particles implying formation within the crucible melt. A Consistent precipitate volume of ~7% over a range of powder particle diameters indicated a consistent atomization process. Occasional voids were observed in GRCop-42 powder. Precipitate size was refined in L-PBF GRCop-42 to a greater extent than in GRCop-84 improving Orowan strengthening, however this benefit was lost after heat treatment due to greater coarsening of precipitates. Precipitates in GRCop-42 accumulated on grain boundaries during heat treatment to a greater extent than in GRCop-84.