Effects of magnetic field and electric current on the solidification of AZ91D magnesium alloys using an electromagnetic vibration technique

摘要

Using an electromagnetic vibration (EMV) technique, we solidified the AZ91D magnesium alloys at different magnetic flux densities and electric current levels when the vibration frequency was kept at 900 Hz so as to find the optimum processing parameters. The microstructure and microtexture of the alloy were examined under various magnetic fields, revealing that with the increase of the magnetic flux density, B_0, the microstructure becomes finer and finer and eventually consists of equiaxed grains with the average diameter approximately 57 mu m at the magnetic flux intensity of B_0 = 10 tesla (T). In terms of the effect of the electric current on microstructure formation, the average grain size first decreases when the effective electric current, J_e, increases from 10 to 60 ampere (A) and then increases when the electric current is further increased from 80 to 120 A. The grain refinement mechanism is clarified when considering the overall EMV process during solidification. The competition between the Lorentz force due to the imposition of the alternating current and the static magnetic force is also incorporated, which is of great importance in elucidating the microstructure and the microtexture formation.