Microstructures of the alloy without treatment

treated by mechanical vibration

ultrasonic and by compound action of ultrasonic and mechanical vibration were investigated comparatively.Influences of pouring temperature and preheating temperature of mold on solidification structure of the alloy after compound treatment of ultrasonic and mechanical vibration were expounded.The results show that primary grain in magnesium alloy AZ91D-3Ca can be refined significantly by compound treatment of ultrasonic and mechanical vibration

which is apparently superior to mechanical vibration treatment or melttreatment by ultrasonic.The second phases with short strips or granular are distributed uniformly at grain boundary

and tensile strength and elongation of the alloy with compound treatment are increased by 79.67%and by 35.71%

respectively.When pouringt temperature is in range of 610

7

00℃

obvious refining effect can be observed at different pouring temperature

however change of microstructure refinement is independent on change of pouring temperature.With the increase of preheating temperature of the mold from 20℃to 600℃

primary phase is converted from incomplete dendrite to equiaxed or rossette-shaped crystal with slight coarseness.