Effect of electromagnetic stirring current on the mechanical properties of Cu-15Ni-8Sn alloy and its mechanism of inducing dendrite refinement and Sn distribution homogenization

Abstract

A Cu-15Ni-8Sn alloy was prepared by electromagnetic stirring (EMS) based on the traditional melting casting method. The effects of electromagnetic stirring current on the dendrite structure characteristics, Sn element distribution, tensile strength, and elongation of the Cu-15Ni-8Sn alloy were studied, and appropriate electromagnetic stirring current parameters were selected. The relationship between the characteristics of the precipitated phase and the orientation of the matrix under the electromagnetic stirring current was analyzed, and the mechanism of fine crystal strengthening induced by the electromagnetic field was discussed. The results showed that EMS was beneficial for dendrite thinning. As the stirring current increased from 0 A to 140 A, the dendrite structure gradually changed to a rosette structure. When the stirring current was 30 A, the minimum secondary dendrite spacing was approximately 35.18 µm, and the grain boundary width was reduced to approximately 10 µm, The Sn element fluctuation range in the matrix was also the smallest, and the precipitate phase was dominated by the CuNi2Sn phase, which had a coherent relationship with the matrix. At this time, the tensile strength and elongation of the alloy were 520.82 MPa and 9.72 %, respectively. The forced flow caused by EMS promoted the temperature field in the melt to become uniform and inhibited the growth of dendrites. The flow of high-temperature molten liquid led to the remelting of dendrite arms, which produced a large number of dendrite fragments, refined the dendrites, and significantly improved the mechanical properties of the alloy.