Abstract:

Cold spray (CS) which has recently become a promising additive manufacturing (AM) technology, was used to fabricate ultra-strong pure copper. In addition, the effects of carrier gas species on the microstructural characteristics, mechanical properties and deformation mechanisms were systemically explored. The CSAM copper manufactured with N₂ carrier gas reveals a heterogeneous bimodal microstructure consisting of ultra-fine grains at the particle interface and relatively coarse grains in inner particles. With He carrier gas, a homogeneous grain structure consisting of ultra-fine grains in most areas was obtained. Compressive tests showed that N₂ and He carrier gasses enabled ultra-high yield strengths of 340 and 415 MPa, respectively. These values are comparable to severely plastic deformed copper, which has extremely low ductility and shape fidelity. On the other hand, both samples showed a strain-softening phenomenon that does not commonly occur at room temperature. The deformation microstructures revealed that dynamic recovery (DRV) and dynamic recrystallization (DRX) phenomena were generated despite being deformed at room temperature. Based on the above findings, the overall deformation mechanisms according to the carrier gas species in the CSAM copper manufacturing process were discussed. Furthermore, the work hardening and softening behaviors of CSAM Cu are predicted by using a constitutive equation.

Key words: Cold spray additive manufacturing, Carrier gas, Pure Cu, Mechanical properties, Deformation behavior