Based on the magnetic-fluid-thermal multiphysics transient coupling numerical simulation results of the magnesium alloy direct-chill (DC) casting, the effects of conventional vibration electromagnetic field (VMF), differential phase vibration electromagnetic field (DP-VMF), conventional low-frequency electromagnetic field (LFMF), and differential phase low-frequency electromagnetic field (DP-LFMF) on melt flow were systematically investigated from the perspective of impulse. Based on thermal behavior and crystal growth theory, the relationships between the velocity field, temperature field, and the morphology of the solidification structure were discussed, and the effect and mechanism of different electromagnetic fields in improving the solidification structure were revealed. Simultaneously, the effects of different electromagnetic fields on AZ31B and AZ80 alloys were investigated. The DC casting experiment verified the theoretical results. Results show that applying low-frequency electromagnetic fields (LFMF and DP-LFMF) can effectively inhibit the formation of columnar grain, but the effect of microstructure refinement is weak; the impact of vibration electromagnetic fields (VMF and DP-VMF) is precisely the opposite. The structure refinement effect of DP-VMF and the inhibition effect of DP-LFMF on columnar grains are better than those of their conventional electromagnetic fields. In the presence of DP-VMF, the average grain size of the center, 1/2 radius, and the edge of the ingot decrease by about 42%, 49%, and 77%, respectively, compared with no electromagnetic field.

Ultrasonic vibration was introduced into the casting of quasicrystal-reinforced magnesium alloy ZW61. The microstructure, mechanical properties, and corrosion resistance were studied. The dual-frequency ultrasonic field (DUF) treatment reduced the α-Mg grain size from 502 µm to 69 µm, and the aggregated lamellar I-phase was refined into tiny dot-like shapes with a smaller area fraction. Static corrosion and electrochemical tests indicated that DUF decreased the corrosion rate from 10 mm·y⁻¹ to 3 mm·y⁻¹ with a denser protective oxide film. DUF not only significantly enlarged the effective cavitation area but also reduced the dependence of transient cavitation on the initial bubble radius. The ratio R_max³/t_c was used to qualitatively characterize the cavitation strength, and cavitation dynamics calculations indicated that DUF had higher cavitation strength compared to single-frequency ultrasonic field (SUF). An equation for corrosion rate versus microstructural parameters (grain size, second phase fraction, potential difference) was developed, which could well predict the corrosion rate of magnesium alloy ZW61 without and with different ultrasonic vibrations.

In this study, the extruded Mg-Zn-Mn-Ce-Ca alloy tube with a low compression anisotropy along the ED, 45ED and TD was prepared. The effect of the second phases, initial texture and deformation behavior on this low mechanical anisotropy was investigated. The results revealed that the alloy tube contains the high content (Mg_1-xZn_x)₁₁Ce phase and the low content of Mg₁₂Ce phase. These second phases are respectively incoherent and coherent with the Mg matrix, and their influence can be ignored. Additionally, the alloy tube exhibited a weak basal fiber texture, where the c-axis was aligned along the 0° ~ 30° tilt from TD to ED. Such a texture made the initial deformation (at 1.0% ~ 1.6% strain) of the three samples controlled by comparable basal <a> slip. As deformation progressed (1.6~9.0% strain), larger amounts of ETWs nucleated and gradually approached saturation in the three samples, re-orienting the c-axis to a 0°~±30° deviation with respect to the loading directions. Meanwhile, the prismatic 〈a〉 and pyramidal <c+a> slips replaced the dominant deformation progressively until fracture. Eventually, the similar deformation mechanisms determined by the weak initial texture in the three samples contribute to the comparable strain hardening rates, resulting in the low compressive anisotropy of the alloy tube.

Magnesium alloys are more widely used at higher temperatures. However, it is not well known whether oxide layer, produced at high temperature, could show corrosion protection. Thus, the corrosion behaviors of oxidized AZW800 alloy were investigated by hydrogen evolution and electrochemical measurements to evaluate effect of oxide layer on corrosion resistance. The results showed that corrosion of removed oxide layer AZW800 alloy showed characteristic of localized corrosion, leaving randomly bulky pits. While reserved oxide layer AZW800 alloy exhibited a relatively uniform corrosion. The results indicated that oxide layer could hinder corrosion of oxidized AZW800 alloy in the initial period of immersion. While subsequently, aggravated corrosion would occur owing to defects of oxide layer and less protective products film. Besides, present of oxide layer eliminated micro-galvanic couple on alloy surface. The synergistic effect of elimination of micro-galvanic couple on alloy surface and alkalization effect transforms localized corrosion into relatively uniform corrosion of alloys.