Influence Of Electromagnetic Stirring On Microstructure And Mechanical Properties Of Mg-Zn-Zr Alloys

The Mg-Zn-Zr series magnesium alloys exhibit low density, high strength, goodtechnology and heat treatment performances, and have been paid more and more attention. Inorder to investigate the influence of electromagnetic stirring technology on the tensile andfatigue behavior of as-cast Mg-6%Zn-0.3%Zr series magnesium alloys, the tensile andlow-cycle fatigue experiments at room temperature for Mg-6%Zn-0.3%Zr alloys with gravitycasting state and with electromagnetic stirring voltage of25V,50V and75V were carried out.The results show that the electromagnetic stirring technology can improve themicrostructure of the as-cast Mg-6%Zn-0.3%Zr alloys, and refine the grains. In addition, therefinement degree of the grains increases with increasing the electromagnetic stirring voltage.With increasing the electromagnetic stirring voltage, the tensile strength, yield strength andelongation of the Mg-6%Zn-0.3%Zr alloys increase. The tensile fracture mode for both gravitycasting and electromagnetic stirring casting Mg-6%Zn-0.3%Zr alloys is brittle fracture. Forboth gravity casting and electromagnetic stirring casting Mg-6%Zn-0.3%Zr alloys, the cyclicstress response behavior exhibits cyclic strain hardening, stability, and softening. At lowerapplied total strain amplitudes, the electromagnetic stirring technology can enhance the cyclicstress amplitude of as-cast Mg-6%Zn-0.3%Zr alloys to some extent. At higher applied totalstrain amplitudes, the electromagnetic stirring technology can obviously improve the cyclicstress amplitude of as-cast Mg-6%Zn-0.3%Zr alloys. Through adding the electromagneticstirring voltage of25V, the fatigue lives of as-cast Mg-6%Zn-0.3%Zr alloys at higher appliedtotal strain amplitudes reduce, but the fatigue lives of the alloys at other applied total strainamplitudes can be slightly prolonged. Through adding the electromagnetic stirring voltage of50V and75V, the fatigue lives of as-cast Mg-6%Zn-0.3%Zr alloys at each applied total strainamplitude get enhanced. For both gravity casting and electromagnetic stirring castingMg-6%Zn-0.3%Zr alloys, the relationship between the plastic strain amplitude and reversal cycles to failure obeys the Coffin-Manson equation, and the relationship between the elasticstrain amplitude and reversal cycles to failure can be well described by the Basquin equation.For both gravity casting and electromagnetic stirring casting Mg-6%Zn-0.3%Zr alloys, thefatigue cracks initiate in a transgranular mode at the free surface of fatigue specimens, andpropagate transgranularly.