Microstructural evolution of AlCu2.4 alloy prepared by electromagnetic stirring

Abstract

The effects of stirring current and stirring frequency on the microstructure of semisolid AlCu2.4 alloy prepared by electromagnetic stirring (EMS) were investigated. The microstructural evolution of the partial remelting semi-solid AlCu2.4 alloy under different stirring currents, stirring frequencies, and isothermal holding time was also investigated. Results showed that with increased stirring current and frequency, the microstructures of semisolid AlCu2.4 alloy evolved from coarse dendrites to fine, small, and quasi-globular solid particles uniformly distributed among the eutectic. Moreover, after partial remelting, these microstructures became smaller and more spherical and were distributed more evenly with increased stirring current and stirring frequency. When the stirring parameters were 30 A and 30 Hz, the average grain size was approximately 80 μ m and the shape factor was about 0.76. During partial remelting, both average particle size and the degree of spheroidization constantly increased with prolonged holding time because of Ostwald ripening. The current coarsening rate constant of the semisolid AlCu2.4 alloy prepared by EMS was 567 μm³s^-1 at 590°C. Comparison between the present work and other literature results indicated that the coarsening rate was associated with the microstructure prior to partial remelting, as well as with the alloy composition.