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.