Research On Electromagnetic Fabrication And Mechanics Properties Of Non-dendritic Microstructure AZ91D Magnesium Alloy With Alloying Elements

Compared with other structural materials, magnesium alloys have many excellent properties and been widely applied in the automobile, IT and aerospace industries. Fabrication of high performance magnesium alloys by means of electromagnetic stirring combined with alloying is an important process in commercial application in the future.In the thesis, a set of rotating permanent magnet electromagnetic stirring device has been designed and manufactured, which is of manipulation of temperature and magnetic field distribution and intension. The evolution process of non-dendritic structure AZ91D slurry at isothermal stirring temperature under electromagnetic stirring has been investigated with the device, the results indicate that primaryα-Mg evolves firstly from fine dendrite to rosette grains and becomes spherical grains at last. Furthermore, effects of process parameters (e.g. rotating speed of magnet barrel, alternation of rotating direction and isothermal stirring temperature) on the microstructure of semisolid AZ91D alloy have been also investigated, which indicate that higher rotating speed of the magnet barrel makes the morphology of primaryα-Mg more spherical, alternation of rotating direction has no obvious effect on the the microstructure of semisolid AZ91D alloy and lower isothermal stirring temperature makes the primaryα-Mg more spherical while some of the grains may combined with each other. The mechanics properties of solidified AZ91D ingot stirred by different stirring process has been studied, the results of which show that isothermal stirring at 570℃and solidifying with the most high cooling rate is the optimal process.Microstructure and properties of AZ91D alloy modified with different content of Ce, La, Ce-rich mish metals and Sb have been investigated. It is found that the alloys modified with 1wt.% content of Ce, La and Ce-rich mish metals have the best tensile stength in the same series alloy modified with same alloy element, while 0.5wt.% is the optimal content to alloys containing Sb. Those alloys which possess highest properties were stirred with the optimal process mentioned above, it is found electromagnetic stirring has obvious effect on the semisolid microstructure of...