Effects of different rotation speeds on microstructure, hardness and corrosion resistance of the Au-Cu alloy

In this work, Au-Cu alloys were prepared using the permanent magnetic stirring method. A pair of permanent magnets driven by a rotating motor was selected to induce the rotating magnetic field. The influences of different rotation speeds on secondary dendrite arm spacing, dendritic segregation, hardness, and corrosion resistance of Au-Cu alloys were investigated. The experimental results revealed that the secondary dendrite arm spacing (SDAS) first decreased with the rotation speed increasing, and thereafter increased due to the sharp decrease of magnetic flux density. Generally, the dendritic structure of alloys can be refined remarkably by a rotating magnetic field, but with a too high rotation speed, the degree of grain refinement was reduced. Moreover, it was found that, the segregation of Au element only was slightly improved, but that of Cu was obviously increased by the permanent magnetic stirring. Along with the refinement of SDAS, the hardness and the corrosion resistance of Au-Cu alloys were significantly increased.