Enhanced strength and ductility in laser powder bed fusion of Cu-Cr-Zr-based composite reinforced by micro-nano dual-scale borides

The laser powder bed fusion (LPBF) of Cu-Cr-Zr alloys exhibit an unexpected elevated-temperature ductility dip phenomenon, posing challenges to achieving new engineering limits. Here, a dual-scale boride reinforced Cu-Cr-Zr-based composite composed of TiB2 microparticles and multi-component (TiZrCr)B2 nanoparticles was fabricated by mixing Cu-Cr-Zr alloy with TiB2 powders during the LPBF process. The (TiZrCr)B2 nanoparticles were formed by the spontaneous adsorption of Ti, Zr and Cr solutes onto the B-atom layer of (Ti/Zr/Cr)B2 surface in the multi-solute liquid melt pool. The uniform dispersion of micro-scale TiB2 and nano-scale (TiZrCr)B2 particles promotes homogeneous dislocation motion, meanwhile, compared to TiB2, the (TiZrCr)B2 exhibits stronger interfacial bonding with the Cu matrix, ensuring the synergy of strength and ductility. Compared to the LPBF-fabricated Cu-Cr-Zr alloy, the corresponding composite exhibits enhanced strength and ductility at 25 and 600°C. Moreover, a good electrical conductivity of 68.1% IACS was obtained in the aged Cu-Cr-Zr-based composite.