Pre-deformation aging strengthening mechanism of Cu-15Ni-8Sn alloys prepared by laser additive manufacturing

The recently introduced concept of "additive manufacturing +" can be used to prepare parts with complex shapes and also high-performance alloys. In this paper, Cu-15Ni-8Sn alloys were prepared by laser powder bed fusion (L-PBF) and laser-directed energy deposition (L-DED), and successively solutionized, 80% cold-rolled, and aged at 400 degrees C. This unconventional process increased the yield strength of L-PBF and L-DED specimens to 1389 MPa and 1317 MPa, with a considerable elongation of 1.9% and 2.8%, respectively. It also greatly shortened the preparation process compared with other methods. The microstructural and mechanical changes of L-PBF and L-DED samples undergone the same pre-deformation aging treatment are consistent. It implies that the pre -deformation aging strengthening mechanism of two kinds of printed samples is basically the same. Pre -deformation changed the morphology and distribution of the spinodal structures and ordered phases, and pro-moted the nucleation of discontinuous precipitates (& gamma;-D03 phase) that preferentially precipitated along elongated grain boundaries and shear bands. This weakened the strengthening effect of D022 and L12 ordered phases. Pre -deformation expedited the aging process, but this was accompanied by a drop in the aging strengthening effect and was more sensitive to the aging temperature. In addition, the stacking faults and L-C dislocations along dislocation cell walls coexisted with the ordered phases for a long time, which inhibited the nucleation of the & gamma; phase and produced a good strengthening effect.