Effects of ultrasonic vibration on microstructure evolution and elevated-temperature mechanical properties of hot-extruded Mg-6Al-0.8Zn-2.0Sm wrought magnesium alloys

The effects of ultrasonic vibration on microstructure evolution and elevated-temperature mechanical properties of hot-extruded Mg-6Al-0.8Zn-2.0Sm wrought magnesium alloys have been investigated. The results show that morphology of relatively coarser Al2Sm phases in the alloy exhibit petal-shaped. However, after being treated by ultrasonic vibration, the Al2Sm phase morphology changes to fine particles. The ultimate tensile strength of the ultrasonic treated Mg-6Al-0.8Zn-2.0Sm alloy at 150 °C has a highest value of 298 MPa and elongation of 20.8%. The maximum pressure caused by transient cavitation is far greater than the shear strength of the Al2Sm phase, which makes the coarse petal-shaped Al2Sm phase break apart into fine polygon particles. Acoustic streaming than makes the broken polygonal Al2Sm particles smooth and uniformly disperse.