Study on phase transformation and solidification microstructure of Y-Co-Cu alloys

Sm-Co rare-earth permanent magnetic, alloys are commonly used in aerospace and automotive power systems due to their good magnetic properties at high temperatures. However, it is accompanied by a high price and waste of rare-earth resources. The addition of rare earth Y and transition metal Cu to the rare earth Sm-Co-based permanent magnets alloy can not only reduce the production cost, but also improve the utilization rate of rare earth resources. To investigate the effects of rare earth Y and transition metal Cu on the phase formation of YCo₅ alloy, Y(Co_1-xCu_x)₅ (x=0.50, 0.10, 0.13, 0.24) alloys were melted by non-consumable tungsten arc melting, and the phase transition and solidification microstructures of Y-Co-Cu alloy were investigated by X-ray diffraction (XRD), scanning electron microscopy-energy dispersive spectroscopy (SEM-EDS) and differential thermal analysis (DTA). Two-phase transformations were observed in Y(Co_1-xCu_x)₅ alloys during the solidification process. Firstly, the primary phase YCo₅ precipitates from the liquid, and then YCu₄ is precipitated from the peritectic reaction L + YCo₅ → YCu₄. The two-phase microstructure with YCo₅ and YCu₄ was formed in the solidification microstructure of Y(Co_1-xCu_x)₅ alloys. With the increase of Cu content in Y(Co_1-xCu_x)₅ alloys, the volume fraction of YCo₅ increases, while the volume fraction of YCu₄ decreases, and the solubility of Cu in YCo₅ increases gradually. The experimental results showed that Cu can be doped smoothly into YCo₅, while the liquidus temperature of the alloy decreases gradually.