| In recent years, in addition to the noise pollution, water pollution, air pollution, solid waste pollution, electromagnetic radiation has become the fifth pollution. Electromagnetic interference(EMI) and electromagnetic pollution is an inevitable problem especially in the electrical and 3c field. Electromagnetic interference shielding materials commonly used is metal materials and polymer composite materials. However, such solutions have the drawbacks of poor mechanical strength, difficult processing, non-recyclability and high cost. Magnesium alloys are the lightest metal structural material, with the advantage of high specific strength and stiffness. The resent studies have shown that magnesium alloy is a kind of potential electromagnetic interference shielding material. However, the use of magnesium alloys in terms of function and structureare is often incompatible. And because of its low absolute strength, the application of magnesium alloys has restrictions. Therefore, we should further enhance the electromagnetic shielding properties of magnesium alloys and improve their strength. It is necessary to research the regular and corresponding mechanism of the effect of alloying on EMI shielding effectiveness(SE) and mechanical properties for Mg alloys in order to promote the integration of function and structure, enhance the value and expand the application of Mg alloy.The study reported different addition of Y, Cu and Y togethered with Ce in Mg-Zn-Zr alloys for obtaining the best alloy composition with good EMI shielding effectiveness(SE) and mechanical properties.① The addition of Y brought about the formation of I-phase(Mg3Zn6Y) and W-phase(Mg3Zn3Y2) with face center structure. With increasing Y content the grains refined and EMI shielding capacity significantly improved in extruded state. The alloy containing 2 wt.% Y exhibited the optimal EMI shielding capacity with the SE value of 79-118 d B related to conductivity and second phase. It was found that good mechanical properties could be achieved by adding very low Y content. The extruded alloy with 0.5 wt.% Y presented higher yield strength(268 MPa), ultimate tensile strength(334 MPa) and good elongation(δ=12.2%). A subsequent aging treatment resulted in precipitation of β1’ and β2’ phases, which led to further improvement in EMI SE.② Cu could effectively refine the grain size of Mg-Zn-Zr alloys and formed Mg Zn C u phase with a face-center cubic structure. EMI SE increased significantly with increasing Cu content in extruded state. This mainly attributed to the low solid solubility of C u in α-Mg martix and the precipitation of Mg Zn C u phases led to recover of partial lattice distortion, thus the relative conductivity enhanced. Therefore, EMI SE improved with increasing C u content. The alloy with 2.5 wt.% Cu exhibited optimal EMI shielding capacity with SE value of 84-118 d B. Meanwhile, it was found that good mechanical properties could be achieved by adding low C u content. The extruded alloy with 0.5 wt.% Cu presented higher yield strength(276 MPa), ultimate tensile strength(346 MPa) and elongation(δ=11.4%). Cu significantly improved the age hardening properties of Mg-Zn-Zr alloy. After Cu addition, the peak aging value reduced from 35 h to 5h.③ Y and Ce addition resulted in the formation of Mg-Zn-Ce and Mg3Zn3Y2(W-phase) as well as a significant grain refinement. It was found that Mg-Zn-Ce was an orthorhombic structure and W-phase was a face-center cubic structure, respectively. Y and Ce addition had an influence on EMI SE. EMI SE first increased and then decreased. It was related to conductivity, solution of rare earth element, and precipitation of second phase in α-Mg matrix. The alloy with 1 wt.% Y exhibited optimal EMI shielding capacity with SE value of 76-118 d B. The extruded alloy with a certain amount of Y and Ce exhibited optimal yield strength(313 MPa), ultimate tensile strength(356 MPa) and elongation(δ=12.1%) compared with extruded Mg-Zn-Zr alloy due to grain refinement and precipitation strengthening. Aging treatment would improve EMI SE of Mg-Zn-Y-Ce-Zr alloys. EMI SE increased with aging time. The 50 h aged Mg-5Zn-0.5Y-0.5Ce-0.6Zr had superior EMI SE with 86-88 d B at 800MHz-1.5GHz. |
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