Microstructure and mechanical properties of Cu-Ni-Sn alloy regulated by trace rare earth element Y

The microstructure and mechanical properties of Cu-12.5Ni-5Sn-xY alloys with different Y addition amounts prepared using spark plasma sintering (SPS) were investigated, and the relationship was discussed. Results indicate that the addition of Y could significantly improve the mechanical properties. When 0.4 wt% Y is added, the maximum hardness and yield strength are approximately 329.5 HB and 691.9 MPa, which are approximately 31 % and 48 % higher than that without Y, respectively. The addition of appropriate amount of Y can significantly refine the grains, promote the transformation of gamma-phase in the alpha + gamma coexisting structure from lamellarshape to needlelike-shape, and significantly inhibit the nucleation and growth of discontinuous precipitation (DP). Especially, when 0.4 wt% Y is added, the nano-scale NiY3 particles precipitated at the grain boundary can hinder the migration of the grain boundary and occupy the nucleation sites of the gamma-phases. In general, grain refinement, nano-precipitation strengthening and inhibition of DP are the main reasons for the improvement of mechanical properties.