The microstructure and mechanical properties of Mg-Y-Zr-xNd alloys with 0–2.63 wt% Nd were investigated using optical microscopy, scanning electron microscopy, transmission electron microscopy, X-ray diffraction and tensile testing test. Results indicated that more Mg24Y5 particles and Mg14Nd2Y (β) phases were dispersed in the matrix when Nd content increased from 0 wt% to 2.63 wt% in the extruded alloys. Consequently, the nucleation of dynamic recrystallization and the volume fraction of recrystallized grains were promoted obviously. The average grain size can be refined in the range of 4.6–1.3 μm after the addition of 2.63 wt% Nd. The tensile strength of extruded alloys increased with increasing Nd content, and elongation exhibited an opposite change tendency. The extruded alloy sheet with 1.01 wt% Nd demonstrates optimal combination of strength and plasticity, i.e., the ultimate tensile strength, yield strength, and elongation were 273 MPa, 214 MPa, and 24.2%, respectively. Variations in mechanical properties are discussed on the basis of microstructure observations.

•A high-strength Mg-5Zn-1Ce-0.5Y-0.6Zr alloy with low RE content was developed.•A high yield strength (407 MPa) and moderate elongation (7.1%) are achieved.•The yield strength is much higher than those of several Mg-Gd-Y series alloys.•The high strength is related to fine grains, precipitates and texture.A new high-strength Mg-5Zn-1Ce-0.5Y-0.6Zr (wt%) magnesium alloy with low rare-earth content was developed by extrusion and direct aging. The peak-aged sample exhibited a yield strength of 407 MPa and an ultimate tensile strength of 421 MPa. The yield strength of this alloy was much higher than those of several Mg-Gd-Y alloys to which large amounts of rare-earth metals were added. The high strength of the alloy was closely related to the combined contributions of ultra-fine dynamically recrystallized grains (about 1 μm diameter), numerous nanoscale precipitates, and a strong basal texture.

The as-cast Mg-Y-Zr-xNd alloys with different Nd contents were prepared, and the effects of Nd content on microstructure, mechanical properties and electromagnetic interference (EMI) shielding properties were investigated. The results show that the grain sizes are refined from 70.1 μm to 45.2 μm, discontinuous bone-shaped β phases are formed mostly in the triple junction of grain boundaries when the content of Nd increases to 2.63 wt%. The mechanical properties and EMI shielding capacity are both enhanced significantly by adding Nd element. The alloy with 2.63 wt% Nd has a good combination of mechanical properties and EMI properties. T6 heat treatment is able to further improve the EMI shielding effectiveness. The above-mentioned experiment results are attributed to the microstructural variation caused by adding different contents of Nd.

The microstructure, dynamic recrystallization, texture, anisotropic behaviour, mechanical properties and electromagnetic shielding effectiveness of Mg–Zn–Zr–Ce alloys were comprehensively investigated in this study. Results indicated that the addition of Ce refined the grains and induced the formation of a Mg–Zn–Ce phase with a unique orthorhombic structure. Dynamic recrystallization was improved when Ce was added because the particle stimulated nucleation mechanism. The random orientation of recrystallization grains weakened the basal texture. The anisotropy index decreased from 1.02 to 0.43 after 1.16 wt% Ce was added. Ce addition enhanced the mechanical properties when the Ce content ranged from 0 to 1.90 wt%, and then decreased with a higher 2.74 wt% Ce content. Electromagnetic shielding effectiveness was also improved initially with the addition of Ce, and then decreased, but was still higher compared with the Ce-free alloy. Good mechanical properties and excellent electromagnetic shielding properties were simultaneously achieved through 1.16 wt% Ce addition. The alloy not only exhibited good yield strength (249 MPa), ultimate tensile strength (316 MPa), and elongation (δ=15%) but also superior electromagnetic shielding effectiveness with 71 dB at 1200 MHz.

A novel low-cost method for melt purification of magnesium alloys, the melt self-purifying technology (MSPT), has been developed successfully based on a low temperature melt treatment (LTMT) without adding any fluxes. The iron solubility in the molten liquid of magnesium and its alloys, and the settlement velocity of iron particles were calculated. It is shown that the low temperature melt treatment is an effective method to decrease the impurity Fe content in magnesium and its alloys. Without any additions, the Fe content in the AZ31 alloy was reduced to 15 ppm from the initial 65 ppm, and the Fe content in the AZ61 melt was decreased to 20 ppm from the initial 150 ppm after the low temperature melt treatment. The results also showed that the Fe content in AM60 and AM50 dropped to 15 and 18 ppm, respectively, from the initial 150 ppm after the low temperature melt treatment. For ZK 60, the Fe content in the melt down to less than 5 ppm was achieved. After the low temperature melt treatment, the Si content in the above alloys was also decreased obviously.

•The second phases were characterized systematically in Mg–Zn–Cu–Zr alloys.•Excellent EMI SE was successfully obtained by adding Cu.•Mechanism of EMI SE was analyzed.•Good mechanical properties could be achieved by adding low Cu content.The microstructure, electromagnetic interference (EMI) shielding effectiveness (SE) and mechanical properties of Mg–Zn–xCu–Zr alloys (x = 0–2.32 wt.%) were investigated in this study. The results indicated that the addition of Cu led to the formation of MgZnCu phase with a face-center cubic structure, and resulted in grain refinement. EMI SE increased significantly with increasing Cu content in extruded state. The alloy with 2.32 wt.% Cu exhibited optimal EMI shielding capacity with SE value of 84–117 dB. Meanwhile, it was found that good mechanical properties could be achieved by adding low Cu content. The extruded alloy with 0.37 wt.% Cu presented higher yield strength (276 MPa), ultimate tensile strength (346 MPa) and elongation (δ = 11.4%) compared with other extruded alloys. However, a higher Cu content would substantially deteriorate tensile properties of the alloys. Based on microstructure observation, the variation of EMI shielding capacity and mechanical properties have been discussed.

The effects of trace Y and Ce additions on the microstructure and mechanical properties of extruded Mg–Zn–Zr alloy sheets were investigated. Results indicated that Y and Ce additions led to significant grain refinement and to the formation of Mg–Zn–Ce, Mg3Zn6Y (I-phase) and Mg3Zn3Y2 (W-phase). Mg–Zn–Ce and W-phase were found to possess an orthorhombic and a face centered cubic structure, respectively. Ultimate tensile strength, particularly yield strength, significantly increased after Y and Ce additions, and good elongation was also achieved. The extruded alloy with 0.28 wt% Y and 0.52 wt% Ce exhibited optimal yield strength (313 MPa), ultimate tensile strength (356 MPa) and elongation (12.1%). With increasing Y and Ce additions, strain hardening rate decreased, and the yield-to-ultimate tensile strength ratio (σs/σb) increased. Variations in mechanical properties were discussed based on microstructure observation.

The effects of Ce addition on microstructure and electromagnetic interference (EMI) shielding response of Mg–6Zn–0.5Zr (ZK60) alloy have been investigated. Ce addition resulted in grain refinement and higher density of Mg–Zn–Ce and MgZn2 intermetallic particles in the alloy. In particular, this was substantially remarkable as the addition of Ce was up to 1.0 wt%. It is interesting to note that as-extruded ZK60 alloy with 1.0 wt% Ce addition exhibited an EMI shielding effectiveness (SE) exceeding 70 dB at the frequency range of 30–1,500 MHz, which was significantly higher than that of ZK60 alloy without Ce addition and reached the requirement of high protection. The superior SE was probably related to the increased reflection and multiple reflection of electromagnetic radiation induced by Ce addition. Direct artificial aging at 150 °C for 25 or 50 h led to a further increase of 7–10 dB in the SE of the alloy with 1.0 wt% Ce addition. The advantages of excellent shielding capacity and favorable mechanical strength make the Mg–Zn–Zr–Ce alloy an attractive shielding candidate material for a variety of technological applications.

•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.

Electromagnetic interference shielding, hardness, and electrical conductivity measurements were employed to evaluate the effect of aging precipitation on shielding characteristics of ZK60 magnesium alloy. During artificial aging MgZn2 phase precipitates occurred and the age hardening peak happened at 150 °C for 15 h. Aging precipitation induced enhanced shielding effectiveness as well as tensile strength in the alloy. It is interesting to note that the shielding effectiveness exhibited a rapid increase with increase in aging time until 15 h, but for longer aging time it tended to remain largely unchanged. Artificial aging at 150 °C for 15 h can thus be considered as the optimum heat treatment condition. In this condition, the good combination of superior shielding effectiveness greater than 70 dB and high mechanical properties was achieved. The origin of the attractive electromagnetic interference shielding properties is discussed based on second phase precipitation in the alloy.Highlights► Aging at 150 °C led to a great elevation in shielding capacity due to numerous precipitates. ► Shielding effectiveness increased with aging time until 15 h, but for longer aging time it remained largely unchanged. ► The alloy exhibited excellent shielding effectiveness higher than 70 dB when aging at 150 °C for 15 h.

Magnesium alloys have a significant advantage, low density over other structure metals currently and have been widely used in various fields such as transportation and aerospace. With the development of research and the enlargement of research scope, more advantages have been developed: high storage capacity, high theoretical volumetric energy density, extraordinarily high damping capacity, good biocompatibility, excellent shielding efficiency as well as impressive thermal conductivity. Therefore Mg alloys have the potential to be various functional materials, such as hydrogen storage material, rechargeable electrochemical batteries, damping material, biodegradable implant material, electromagnetic shielding material, and thermal conductive material. Unfortunately, each kind of functional material has bottlenecks needing to be broken through, and a lot of researches have to be carried out. This review comprehensively covers the research progress and the up-to-date summary of Mg and Mg alloys as functional materials in recent years. The six kinds of functional materials above all will be discussed.

The research and development status of casting magnesium alloys including the commercial casting alloys and the new types casting alloys are reviewed, with more attention to microstructure and mechanical properties of modified-AZ91, AM60 and WE43 alloys with various additions, and new types of low cost casting alloys and high strength casting alloys. The modification and/or refinement of Mg2Si phase in Mg–Al–Si based casting alloys by various additions are discussed and new purifying technologies for casting magnesium alloys are introduced to improve the performance. The modified AZ81 alloy with reduced impurities is found to have the tensile strength of 280 ± 6 MPa and elongation of 16% ± 0.7%. The fatigue strength of AZ91D alloy could be obviously improved by addition of Ce and Nd. The Mg–16Gd–2Ag–0.3Zr alloy exhibits very high tensile and yield strengths (UTS: 423 MPa and YS: 328 MPa); however, its elongation still needs to be improved.