Phase morphology is one of the most important microstructural characteristics determining the mechanical properties and therefore, the service performance of polycrystalline materials. The effect of ultrasonic treatment on the β-phase (Mg17Al12) morphology of Mg–9·0Al alloy is studied in the present paper. The result shows that with high intensity ultrasonic vibration employed during the solidifying of Mg–9·0Al, the β-phase in the entire cross-section of the billet is significantly refined and also changed from continuous to discontinuous morphology. Spherical β-phase is formed during the solidification of billet treated with high intensity ultrasonic vibration.
