Light metals are gaining increased attention due to ecological sustainability concerns and strict emission regulations. Magnesium (Mg) is one such metal that has the potential to replace high density components, which can reduce emissions through lightweighting. However, the mechanical properties of Mg alloys must be improved for them to become viable candidates for structural applications. To this end, the current study examines the effect of sonication vibrational amplitude on the microstructure and mechanical properties of AZ91E Mg alloy. The molten alloys were subjected to ultrasonic treatment at a frequency of 20 kHz, 180 s of processing time and vibrational amplitudes ranging from 1.25 to 15 µm. The resultant castings were characterized using optical microscopy, scanning electron microscopy and tensile testing. It was found that sonication with amplitudes up to 7.5 µm was able to effectively refine the secondary phases of the alloy. Similar trends were observed for grain size and yield strength. The refinement in microstructure was likely caused by the finer grain size and cavitation induced undercooling of the liquid metal. In addition, it was also noted that even the lowest level of amplitude (1.25 µm) was able to increase the density, improve the ultimate tensile strength and ductility of the castings. The tensile strength and ductility were thought to have been enhanced by ultrasonic degassing and refinement in microstructure, while the yield strength was improved through the Hall-Petch effect. The results from this study provided a basis for optimizing the sonication process and promoting its use in industry. As a result, Mg alloys improved through ultrasonic processing have the potential to replace higher density components, with consequent energy efficiency and environmental and ecological benefits.

由于生态可持续性问题和严格的排放法规，轻金属越来越受到关注。镁 (Mg) 就是这样一种金属，它有可能取代高密度部件，从而通过轻量化减少排放。然而，必须提高镁合金的机械性能才能使其成为结构应用的可行候选者。为此，本研究考察了超声振幅对 AZ91E 镁合金微观结构和力学性能的影响。对熔融合金进行超声波处理，频率为 20 kHz，处理时间为 180 秒，振幅范围为 1.25 至 15 µm。使用光学显微镜、扫描电子显微镜和拉伸测试对所得铸件进行表征。结果发现，振幅高达 7.5 µm 的超声处理能够有效细化合金的第二相。在晶粒尺寸和屈服强度方面也观察到了类似的趋势。微观结构的细化可能是由更细的晶粒尺寸和空化引起的液态金属过冷引起的。此外，还注意到即使是最低水平的振幅 (1.25 µm) 也能够增加密度，提高铸件的极限抗拉强度和延展性。超声波脱气和微观结构细化提高了拉伸强度和延展性，而霍尔-佩奇效应提高了屈服强度。该研究结果为优化超声处理工艺和推广其工业化应用提供了依据。因此，