Microstructures and properties of SLM-manufactured Cu-15Ni-8Sn alloy

Easily segregated Cu-15Ni-8Sn alloy bulk material was fabricated using a selective laser melting (SLM) process. The microstructure of SLM-manufactured Cu-15Ni-8Sn alloy was investigated using optical microscopy (OM), scanning electron microscopy (SEM), X-ray diffraction (XRD), and transmission electron microscopy (TEM). Differences in the microstructures and elemental segregation of gas-atomized alloy powder, cast ingots, and SLM-manufactured samples were analyzed. The statistical average grain size of the SLM-manufactured Cu-15Ni-8Sn alloy was 4.03 μm. Microstructures of the SLM-manufactured sample were mainly composed of epitaxially grown slender cellular structures with submicron widths. Microsegregation was detected by TEM, and 80- to 200-nm Sn-enriched precipitates were dispersed between cellullar structures. Many dislocations and dislocation tangles appeared around the precipitates. An EBSD test revealed that most local misorientations within 3 degrees were concentrated in fusion line regions. Compared with cast ingots, the yield strength Rp0.2, ultimate tensile strength Rm, elongation A, and elastic modulus Eof the SLM-manufactured sample increased by 67%, 24.6%, 360%, and 7%, respectively. Moreover, the SLM-manufactured Cu-15Ni-8Sn alloy could be directly aged at 350℃ for 12 h, reaching Rm = 991.1 MPa and A =3 %, with no need for solid solution treatment or cold working.