Technical And Theoretical Research Of Electromagnetic Stirring On Solidification Structure Of Aluminum Alloys

In order to improve material properties and develop new research directions, improving themicrostructure of alloy by solidification process is become a mainstream way in the materialsscience field. Due to non-contact and non-pollution, keeping the alloy’s composition, easiercontrolling process and significant effect, electromagnetic stirring technology has a contribution tomake industrial production easier. Therefore, it is high valuable to study the solidification processandmaterials’ propertiesvariation underelectromagneticfields.Aluminum alloys in our lives has been regularly applied. Controlling solidification process ofaluminum alloys by electromagnetic stirring technology has been numerous studied, someachievements have been applied in industrial production. However, the electromagnetic stirrer arewidely exist shortcomings like high energy consumption and weak electromagnetic induct.Because of different views of the grain refinement mechanism in EMS, it’s necessary to improvethe design of EMS and explore new winding ways of its coil. Then the low efficiency ofelectromagnetic induct would be solved. Meanwhile, through the complete experiment anddiscussing mechanism of stirring melt under electromagnetic fields to consummate the metalsolidificationtheory.In this thesis, the Al-Mn alloy was selected as object to study the effect of electromagneticstirring. The single-chain winding way was used to make EMS. The cooling method of coils,stirring frequency, calculation of magnetic field and distribution regularity of the melt velocitieswere studied. Effects of different electromagnetic stirring technology during solidification processhave been researched, as well as the forming and growing mechanism of grain and hardnessperformance.Results shows that a large decrease in grain size is caused by the effect of electromagneticstirring, and the best pouring temperature is710℃. The main reason of grain refining is increasingthe number of effective nucleation sites and the nucleation rate, which restrain the growth rateinversely. The average equivalent diameter of grain decreases with increasing stirring frequencyunder the single rotary electromagnetic stirring. The aluminum alloy grain will be smaller when thestirring frequency is30Hz, to continue increasing the stirring frequency to40Hz, the averageequivalent diameter of grain increased too. Alternating electromagnetic stirring has the better effect than single rotary electromagnetic stirring. The grain size of aluminum alloy will be the smallestwhen the interval time is4seconds under alternating stirring, besides the hardness performance ofAl-Mn alloy can be significantly improve by25%, which is the best hardness performance. Tocontinue increasing the interval time to6seconds, the average equivalent diameter of grain will beincreasedas well.