Microstructure of Mg7Zn3Y0.55Zr Ribbon Made by Single Roll Casting

The ribbons of melt-spun Mg7Zn3Y0.55Zr alloy were obtained by single roll casting technology with different spin speed.The thickness of ribbons was measured.The microstructures of ribbons were studied.The results show: with increase of the spin speed,the thickness of ribbons becomes thinner and thinner.The rapid solidified microstructure of melt-spun magnesium alloy can be divided into three crystal zone through the thickness section: the fine equiaxed zone near the roll surface,the inner columnar zone and the outer equiaxed zone near the free surface.As increase of the spin speed,the grains in the zone near the roll surface become finer and finer.XRD results show there exist Mg_3Y_2Zn_3 phase in all ribbons.Furthermore,for the speed of(1 200 r/min),there exists Mg_2Zn_(11) phase,for speed of 500,800,1 500、1 800 r/min,there exist Mg_(12)YZn phase.