Indexed by:Journal paper Journal:Additive Manufacturing Discipline:Engineering First-Level Discipline:Material Science and Engineering Document Type:J Key Words:Cu-15Ni-8Sn alloy；Laser powder bed fusion (LPBF)；Heterogeneous microstructures；Deformation behavior；Strengthening mechanisms Date of Publication:2022-03-01 Impact Factor:10.998 Abstract:Cu-15Ni-8Sn alloy with layer-by-layer periodic heterogeneous microstructures composed of ultrafine equiaxed (~2.6 μm) and coarse columnar (~12.8 μm) grains was successfully fabricated by laser powder bed fusion (LPBF) additive manufacturing. The microstructures were composed of Sn-depleted α-Cu (Ni, Sn) matrix and Sn-rich γ-(CuxNi1-x)3Sn nano-precipitates. The γ nano-precipitates were found to be mainly uniformly distributed at the melt pool boundaries due to Sn reverse segregation, as though the densely distributed seeds on the surface of a strawberry. The interesting periodic bi-modal microstructure exhibited a simultaneous positive effect on the enhancement of strength and ductility. The yield strength, ultimate tensile strength and elongation at break were (474.04±2.88) MPa, (584.36±4.74) MPa and (14.29±1.78)%, respectively. Remarkable improvements of 12% and 286% in the yield strength and elongation at break were achieved compared with those cast counterparts reported in the published literature. The high dislocations density (~6.78×1014 m-2) were the dominant source of high strength and contributed ~49% to the yield strength according to the theoretical calculation. Massive dislocation cells were generated around the γ nano-precipitates during tensile deformation, improving the dislocation storage capacity and the work hardening ability. These findings validated the LPBF printability and the property enhancement of Cu-15Ni-8Sn and provided a promising strategy for the design of high strength and ductility copper alloys through layered precipitation microstructures. Links to published journals:https://doi.org/10.1016/j.addma.2022.102726