Precipitate Size in GRCop-84 Gas Atomized Powder and Laser Powder Bed Fusion Additively Manufactured Material

Abstract

Laser powder bed fusion (LPBF), also known as selective laser melting, of Glenn Research Copper 84 (GRCop-84), a Cr₂Nb (8 at. % Cr, 4 at. % Nb) precipitation-hardened alloy, produces a fully dense, high-conductivity alloy with tensile strength (470-MPa yield and 710-MPa ultimate tensile strength) superior to other competing copper alloys. Agglomeration and coarsening of precipitates in gas atomized GRCop-84 powder occurred above a threshold of 17 μm in diameter. Area of precipitates within cross sections is consistent among powder particles of different diameters indicating a consistent atomization process. Precipitates within gas atomized powder were shown to either melt and subsequently re-precipitate as the melt pool rapidly cools or break apart during LPBF resulting in precipitates smaller than in the initial powder. Precipitate size in powder therefore does not affect precipitate size, and thus tensile strength, in LPBF GRCop-84.

Keywords:

• Additive manufacturing
• GRCop-84
• laser powder bed fusion
• powder precipitates

Acknowledgments

This work is supported by the U.S. Department of Energy, Office of Science, Office of Fusion Energy Sciences, using User Facility DIII-D, under award number DE-FC02-04ER54698. This work made use of the Materials Research Science and Engineering Center Shared Experimental Facilities at Massachusetts Institute of Technology supported by the National Science Foundation under award number DMR-14-19807. Data, images, and code used to recreate results in this paper are available online in digital format (https://doi.org/10.17632/y4t5g7c4z5).