Research On Microstructure And Properties Of Mg Alloy Under Electromagnetic Field

With people paying attention to the environmental protection, the energy and thedeveloping of digital process, magnesium alloy, which is the lightest metal material inactual application, attracts much attention in automotive industry and 3C productfields because of its excellent physical and mechanical properties.This work is a part of the items, solidification of Mg alloys underelectromagnetic fields, in the Fundamental Research Program of Hubei Province(2004CA005). The effect of electromagnetic fields on the solid solubility andmacro-segregation of alloying elements, the microstructures and solidificationstructures, and the mechanical properties on T6 condition of Mg alloy were allstudied. And the mechanism of solidification of Mg alloy was discussed. The purposeof this work is, to provide new fundamental knowledge for EPM theories and basisfor EPM technology. The following results were obtained.Microstructures of alloys and solid solubility of elements were observes andstudied by means of optical microscope (OM), scanning electron microscope (SEM),energy dispersive spectrometer (EDS) and X-ray diffract analyzer (XRD) and so on.The experimental results showed that, comparing with the sample solidified withoutmagnetic field, microstructures and solid solubility changed significantly. Theaverage grain size off alloys reached the minimum, the homogenization degree ofgrain size increased significantly; almost all of theβ-Mg₁₇Al₁₂ phase breaked intodiscontinuous ones; and magnetic field changed the morphology of (Ce,La)Al₄ phasefrom rod-like to needle-like, without changing its type.The mechanical properties on T6 condition were detected by W60 universal testing machineand HB3000 stiffness detection system, and the linear relation was presented between grain sizeand mechanical properties by regression analysis. The experimental results showed that when themagnetic induction is 0.29T, the yield strength, tensile strength and hardness of AZ91D alloyreached to the maximum, up 12%, 9% and 31%, and the best elongation is got at 0.12T, up 36%;the elongation of AZ91D-0.8%RE in T6 state achieves 2.2% at 0.29T, up 16%. Meanwhile, theyield strength and the tensile strength of alloy increase, and the hardness decreases slightly.Regression analysis showed that the relationship between grain size and mechanical properties isin agreement with Hall-petch expression.