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This study examined the effect of steady magnetic field on the microstructure and mechanical properties of Mg–Zn–Y alloy reinforced by icosahedral quasicrystal phase. Results show that the microstructure of Mg–Zn–Y alloy was further refined as the magnetic field intensity increased. However, the primary α-Mg gradually became coarse over a certain value. No significant effect on the refinement of icosahedral quasicrystal phase was observed. The plane of the alloy treated by steady magnetic field was substituted by the (0002) plane as the primary plane. The plane was intensified gradually as the intensity of the magnetic field increased. The mechanical properties of Mg–Zn–Y alloy also improved with steady magnetic field treatment.This paper is part of a thematic issue on Light Alloys.

Effects of pulsed magnetic field (PMF) on microstructure, mechanical properties and bio-corrosion behavior of Mg-7Zn alloy were investigated. Results show that the solidification microstructure of Mg-7Zn alloy was further refined with increasing discharging voltage. The second phase was changed from discontinuous reticular to island-like and particle-like morphology. Moreover, the volume fraction of second phase in the alloy treated by PMF was reduced. With PMF treatment, the mechanical properties of Mg-7Zn alloy were also enhanced. The PMF treatment was beneficial to the bio-corrosion resistance improvement of Mg-7Zn alloy. The corrosion rate of Mg-7Zn alloy was gradually decreased with increasing discharging voltage.

Pulsed magnetic field (PMF) has been imposed during solidification of Mg-Zn-Y alloy containing icosahedral quasicrystals phase (I-phase) in this work. The effects of vibration power on the solidification microstructure and mechanical properties of Mg93Zn6Y alloy were studied. The results show that the solidification microstructure of the Mg93Zn6Y alloy was further refined with increasing vibration power. The primary α-Mg in the alloy treated by PMF was changed from dendrites with the average grain size more than 1 mm untreated by PMF to rosette-like and polyhedral morphology with the average grain size of 122 μm. Moreover, the I-phase was changed from continuous thick skeletal to discontinuous fine reticular and particle-like morphology. The fraction of I-phase in the alloy treated by PMF was also reduced due to the increase of concentrations of Zn and Y elements inside grains. The mechanical properties of Mg93Zn6Y alloy treated by PMF were also improved significantly. The yield strength, ultimate tensile strength and elongation of the alloy treated by PMF at a vibration power of 350 W at room temperature were 162 MPa, 221 MPa and 1.99%, which were increased by 65%, 66% and 124% respectively, compared to those of the alloy untreated by PMF.

An Al-3Nb-1B master alloy has been prepared using a melt reaction method. The microstructure of the master alloy and its refinement performance on AZ91D magnesium alloy were investigated. Experimental results showed that the Al-3Nb-1B master alloy was mainly composed of α-Al and NbB2 phases. With the increase of the addition amount of Al-3Nb-1B master alloy, the primary α-Mg grains of AZ91D magnesium alloy were further refined. Upon adding 0.5 wt pct Al-3Nb-1B master alloy, the average grain size of the primary α-Mg decreased from 240 to 52 μm. The present results indicated that NbB2 can act as effective heterogeneous nucleus of the primary α-Mg, which accounted for the good grain refining performance on AZ91D magnesium alloy. Compared with the unrefined alloy, the yield strength, ultimate tensile strength, and elongation of AZ91D magnesium alloy refined by 0.5 wt pct Al-3Nb-1B master alloy were increased by 18.4, 15.7, and 27.3 pct, respectively due to the grain refinement effect.