Laser directed energy deposition of Cu-Cr-Zr alloy: Microstructure evolution and its influence on properties

• A decrease in V s enhances molten pool stability and promotes better surface quality. • Based on CET model, the grain evolution during L-DED process was discussed. • Properties were enhanced by nanotwins and in-situ precipitated Cr phase during deposition. Laser directed energy deposited (L-DEDed) Cu alloys present substantial advantages for manufacturing thermal management devices without potential constraints on size. Herein, the printability, microstructure, and properties of a L-DEDed Cu-Cr-Zr alloy were investigated. Decreased scanning velocity facilitates the manufacture of single-track deposit with continuous and smooth surface morphology owning to the diminished Marangoni effect caused by a lower temperature gradient. A heterogeneous grain structure, characterized by an alternating distribution of equiaxed and columnar grains, was achieved in the thin-walled deposit, while a fully columnar grain was obtained in the bulk deposit. Under the effect of thermal cycling, numerous secondary Cr phase in-situ precipitated, and a small proportion of nano-sized annealing twins appeared in both the thin-walled and bulk deposits. In comparison, benefiting from nanotwins and more significant dispersion strengthening from secondary Cr precipitates, the thin-walled deposit exhibited a superior balance of tensile strength (∼337 MPa) and conductivity (∼63.6 % IACS).