Gas Atomization of Copper-based powders for Additive Manufacturing

Copper-based alloys show an attractive combination of electrical conductivity, thermal conductivity, and mechanical properties and in specific applications can be used as tooling materials as well. The Cu-Be alloy, despite hardening upon heat treatment requires a substitute due to health-related hazards associated with its production. The Cu-Ti alloy system is considered a suitable replacement and has been a subject of research for a while now. In this work, powders of Cu-Ti (1.5 wt.% and 3 wt.% Ti) and Cu-Ti-Ni (3 wt.% Ti with 2 wt.% Ni and 5 wt.% Ni) alloys were produced via vacuum induction inert gas atomization (VIGA) —yielding high fractions of sub-250 μm powder (≈93–98 vol.%). After determining the atomization yields in different particle size distribution ranges, the structural, chemical, morphological and rheological properties of the powder have been characterized by XRD, DSC, SEM/EDS, and shear cell rheometry. The processability of Cu-3 wt.% Ti and Cu-3 wt. % Ti-5 wt.% Ni powders was studied by laser powder bed fusion (LPBF) using a commercial red laser printing facility—an especially challenging configuration for copper due to high reflectivity and thermal conductivity. The results showed that VIGA can yield more than 50 wt.% of highly spherical powders in the 20 - 63 μm range suitable for LPBF in a single atomization run. It was found that the fast cooling during atomization suppressed the formation of the β′-Cu4Ti phase, which is the primary strengthening phase for these alloys (after heat treatment). NiTi-based intermetallics can form despite the high cooling rates. LPBF trials were conducted on two representative feedstocks (Cu–3Ti and Cu–3Ti–5Ni) across a 15-point parameter matrix to map densification and microstructure. Scanning speed emerged as the dominant lever for both relative density and hardness; insufficient energy led to lack-of-fusion, whereas high power/low speed promoted keyhole instabilities, with oxide-laden spatter identified as the main defect source. Since the cooling rates in LPBF are too high for the formation of the β′ phase, the Cu-3Ti-5Ni alloy was found to have higher hardness than the Cu-3Ti alloy in the as-printed condition. This is in contrary to earlier studies on cast and wrought alloys. In the as-printed condition, Cu–3Ti–5Ni achieved ≈30–45% increase in hardness relative to Cu–3Ti, consistent with the strengthening from NiTi-type phases when the β′-Cu4Ti phase is absent. Post-printing ageing increased hardness for Cu–3Ti from 160 to 281 HV, via β′-Cu4Ti precipitation while Cu-3Ti-5Ni reached a maximum of 253 HV. Future work should couple tensile and electrical conductivity measurements with further process optimization to fully compare these alloys against established copper systems.