Microstructure, electromagnetic shielding effectiveness and mechanical properties of Mg–Zn–Y–Zr alloys

•The second phases were characterized systematically in Mg–Zn–Y–Zr alloys.•Adding yttrium improved EMI SE and mechanical properties in the extruded state.•A subsequent aging treatment could further enhance EMI SE.

The microstructure, electromagnetic interference (EMI) shielding effectiveness (SE) and mechanical properties of Mg–Zn–Y–Zr alloys with 0–3.91 wt.% Y were investigated systematically in this work. The results indicated that addition of Y brought about the formation of I-phase (Mg3Zn6Y) and W-phase (Mg3Zn3Y2) and refined grains in as-cast state. After hot extrusion, there was more and more broken particles dispersing in matrix when Y content ranged from 0 to 3.19 wt.%. With increasing Y content, EMI SE was enhanced significantly in extruded state. The alloy with 1.9 wt.% Y exhibited the optimal EMI shielding capacity with the SE value of 79–118 dB. 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 = 12.3%) compared with other extruded alloys. A subsequent aging treatment on the extruded alloy with 1.29 wt.% Y exhibiting outstanding comprehensive EMI SE and mechanical properties resulted in precipitation of W, β1′ and β2′ phases, which led to further improvement in EMI SE. The peak-aged sample showed the superior mechanical properties. Based on the microstructure observation, the changes of EMI shielding capacity and mechanical properties have been discussed.