Affiliations: [a] Department of Mechanical Engineering, Xi'an Jiaotong University, Xi'an, Shaanxi, China | [b] Department of Mechanical, Materials and Aerospace Engineering, Illinois Institute of Technology, Chicago, IL, USA
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.
