The effects of Zn and Cu addition on the microstructure and mechanical properties of the extruded Mg-3Sn-1Ca alloy were systematically studied. The effects of the grain size, texture, type and distribution of the second phase on the mechanical properties of the alloy were analyzed. The mechanical test results show that the addition of Zn and Cu elements can significantly improve the mechanical properties of the alloy. The as-extruded Mg-3Sn-1Ca-1Zn-1Cu alloy has the best comprehensive mechanical properties, and the UTS, YS and E_L are 244 MPa, 159 MPa and 13.4%, respectively. Compared with the Mg-3Sn-1Ca alloy, the UTS and E_L of the Mg-3Sn-1Ca-1Zn alloy are increased by 50 MPa and 132%, respectively. However, the UTS of the TXC311 alloy is increased by 55 MPa, but the ductility of the Mg-3Sn-1Ca-1Cu alloy is far less than that of the Mg-3Sn-1Ca-1Zn alloy, which is mainly attributed to the presence of a large amount of hard and brittle Mg2Cu phase in the alloy. Interestingly, the addition of Zn to Mg-3Sn-1Ca-1Cu alloy can improve the elongation of the alloy, which is due to the solid solution strengthening caused by the Zn element and the formation of small MgZnCu phase with Zn element and the consumption of Mg2Cu phase.

In this paper, the effect of Ca and Zr additions on microstructure and mechanical properties at room temperature of Mg-Sn alloys was investigated by comparison of Mg-3Sn (wt.%) (T3), Mg-3Sn-1Ca (wt.%) (TX31), and Mg-3Sn-1Ca-1Zr (wt.%) (TXK311) alloys under extrusion. The results show that the main phases of as-extruded T3 alloy were α-Mg and Mg₂Sn phases, while the CaMgSn phase was formed and the precipitation of Mg₂Sn phase was inhibited in the TX31 and TXK311 alloys due to the addition of the Ca element. Zr did not form intermetallic compounds with other elements but dissolved in the grains of the matrix and became nucleating particles. Incomplete dynamic recrystallization (DRX) occurred in all alloys during hot extrusion. The coarse rod-like and fine block-like mixed CaMgSn phase was observed in α-Mg matrix of as-extruded samples of the TX31 alloy, and the dispersed granular CaMgSn phase was observed in the TXK311 alloy. Ca inhibited the dynamic recrystallization behavior of the alloys, while Zr promoted the dynamic recrystallization behavior. All the as-extruded alloys exhibit typical fiber texture of {0001} basal//ED. With the addition of Ca and Zr elements, the particle stimulated nucleation (PSN) effect excited by the second phase particles gradually weakened the texture. TXK311 alloy has good comprehensive mechanical properties at room temperature, with tensile strength, yield strength, and elongation of 261 MPa, 244 MPa, and 11%, respectively, and the average grain size was 1.8 μm. Grain refinement and second phase dispersion strengthening are considered to play critical roles in the strength optimization of the TXK311 alloy.

The effects of ultrasonic power, treatment time and holding time on AZ80 magnesium melt purification by ultrasonic field were studied. The results indicate that ultrasonic treatment can accelerate the separation of inclusions and attain melt purification. When the magnesium alloy melt is treated with ultrasonic power 80 W at 650 °C for 60 s and holding 100 s, the best melt purification is achieved. Moreover, the effect of ultrasonic degassing on AZ91 alloy was also investigated. When the ultrasonic power is 150 W for 90 s, the hydrogen content and degassing efficiency are 9.6 cm³/100 g and 50.5%, respectively. The corresponding mechanical properties are R_m = 194 MPa, R_0.2 = 133 MPa and A = 4.8%, respectively, and the mechanisms of purification and degassing were analyzed because of the cavitation effect.

The effect of ultrasonic treatment parameters, including ultrasonic treatment duration, frequency resonance, and treatment temperature, on the degassing of Mg-3.03Ca alloys was investigated. The results indicated that the optimum degassing efficiency could be obtained under the ultrasonic resonant condition. When applying ultrasonic treatment for 90 s with 150 W at 700 °C, the minimum hydrogen content and the highest degassing efficiency are obtained, respectively (42.8 cm³/100 g and 27.5%). The ultrasonic treatment can remove the gas from the melt and refine the microstructures. Finally, the mechanism of ultrasonic degassing and refinement was analyzed.

The effects of 1% Zn on the corrosion properties of homogenized Mg-3Sn-1Ca-1Cu alloys were investigated. The corrosion behavior of homogeneous TXC311 and TXCZ3111 alloys in 3.5% NaCl solution was studied by using a hydrogen evolution test, polarization curve and impedance spectrum, and the corrosion properties of the alloys were discussed with considerations relative to microstructure. The results show that the second phases of TXC311 alloy consist of CaMgSn and Mg₂Cu. The corrosion rate is 132 mm·year⁻¹. After the addition of 1% Zn element, the grains are significantly refined, the number of Mg₂Cu phases is reduced and the MgZnCu phases are formed. The corrosion rate of Mg-3Sn-1Ca-1Cu alloy decreased to 80 mm·year⁻¹. TXCZ3111 alloy presents fine grains and a reduced number of Mg₂Cu phases, which improve the stability of the corrosion film and reduce the corrosion rate of the alloy. Therefore, the corrosion resistance of TXCZ3111 alloy is much higher than that of TXC311 alloy.