Effects of some treating technologies

such as without magnetic field treatment

with pulsed magnetic field treatment

alternate magnetic field treatment and compound treatment of pulsed magnetic field and alternate magnetic field

on solidified structure and mechanical properties of AZ31 magnesium alloy were investigated comparatively.Morphology of primary phase and grain size of the alloy with different pulse voltage

pulsed frequency and mould temperature under the conditions of compound treatment were obserevd.The results show that refinement effect of solidified structure by compound treatment is more efficient than that of pulsed magnetic field treatment or alternate magnetic field treatment.Average grain size of the alloy can be refined from 3.5 mm to 0.93 mm

and the fraction of equixed grains in the alloy can be increased from 55.8%to 97% by compound treatment.With the increase of the pulsed voltage or frequency

primary phase in the alloy is degraded gradually from well-developed dendrites into fine equiaxed grains or rosette crystals.When the mould temperature is at 20

6

00 ℃

with the increase of mould temperature

solidified structure is refined firstly and then coarsened

and at 200℃

the grain size reaches the minimum value.For three treatment ways

compound treatment exhibits the best effects.Compared with those of conventional casting

tensile strength and elongation of the alloy are increased by 35.8% and 25.6%

respectively.