Abstract:

Achieving excellent electromagnetic interference (EMI) shielding effectiveness (SE) in high rare earth (RE)-content Mg alloys is currently a significant technical challenge. This work systematically investigated the effects of different Nd elements on the electrical conductivity and EMI SE of Mg-12Gd-3Y-xNd alloy by adding Nd elements to the high RE content Mg-12Gd-3Y alloy, followed by a combined process of hot rolling and aging (R-A). The results indicate that the addition of Nd elements leads to reduced solid solubility of Gd and Y, resulting in a large amount of precipitation. The Mg-12Gd-3Y-2.0Nd alloy has the optimum EMI SE after 63% R-A treatment, reaching 88-118 dB at 30-1500 MHz. The Mg-12Gd-3Y-xNd alloy has acicular and granular forms of the Mg₅(Gd, Y, Nd) (abbreviated as Mg₅RE) phase after R-A treatment. The granular Mg₅RE phase gradually breaks up and refines into more minor scales with increasing rolling reduction and is diffusely distributed in the matrix. The acicular Mg₅RE phase is densely arranged, with cross-distribution in some areas. The cross-distributed acicular Mg₅RE phase, the delicate granular Mg₅RE phase, and the dense β′ phase provide more interfaces for reflecting electromagnetic waves and increase the multiple reflection loss of incident electromagnetic waves. In addition, the Mg-12Gd-3Y-xNd alloy deflects most of the c-axis of the grains parallel to the normal direction (ND) as the rolling reduction increases, making the impedance difference between the plate surface and air larger. The increased impedance makes the material reflect more loss to incident electromagnetic waves. The combined use of these two leads to an excellent EMI SE of Mg-12Gd-3Y-xNd with high RE content after R-A treatment.

Key words: Mg-Gd-Y-Nd alloy, Acicular phase, Granular phase, Electrical conductivity, Electromagnetic interference shielding effectiveness