Effect of Rotating Magnetic Field on Microstructure and Mechanical Properties of Cu-6Ni-6Sn Alloy

In this paper, the effects of rotating magnetic field (RMF) excitation current intensity on Sn segregation, grain refinement, and mechanical properties of Cu-6Ni-6Sn alloy were systematically investigated. The results demonstrate that the application of RMF can effectively refine the as-cast microstructure and mitigate Sn macro-segregation. The average grain size of the as-cast Cu-6Ni-6Sn alloy decreases monotonously with the increase in the excitation current, from 1563 ± 502 μm at 0 A to 207 ± 112 μm at 120 A. In addition, it was found that the difference in Sn content in the radial direction of the ingot reduced from 3.9 wt.% to 1.0 wt.%. The RMF improves heat transfer through forced convection, reduces temperature gradients and alleviates solute enrichment. It increases both thermal undercooling and the growth restriction factor to hinder grain growth and reduces constitutional undercooling to suppress segregation. In addition, the application of the RMF can synergistically increase the tensile strength and the elongation of the as-cast Cu-6Ni-6Sn alloy, with the values changing from 349 ± 4 MPa and 36.9 ± 0.8% at 0 A to 413 ± 4 MPa and 42.8 ± 0.9% at 80 A, respectively. This work quantitatively reveals the coupling relationship between RMF excitation current, grain refinement degree and Sn macro-segregation homogenization in Cu-6Ni-6Sn alloy, and quantitatively clarifies the dominant grain-boundary strengthening mechanism of the alloy under RMF.