Al-CeO2-Mg refiner on grain refinement, cast fluidity and mechanical properties of AZ91 alloy

Grain refinement is a satisfying method to enhance the comprehensive performance of Mg alloys, and using grain refiners to improve the quality of Mg castings has become a common practice in the current casting industry. In this study, the effects of Al-CeO2-Mg grain refiner addition on microstructure, cast fluidity, and mechanical properties of AZ91 alloy were systemically investigated by OM, SEM, DSC, TEM, sand Archimedean spiral mold fluidity test, and tensile test. The results show that the Al-CeO2-Mg grain refiner has a remarkable effect on as-cast AZ91 alloy including notable grain refinement, enhancement of cast fluidity, and improvement of tensile properties. The average grain size of AZ91 alloy is refined by 63% with 1.0wt.% Al-CeO2-Mg grain refiner. Meanwhile, the casting flow length of the as-cast AZ91 alloy is increased from 332 mm to 440 mm. The improvement of cast fluidity is attributed to the decreased liquidus temperature, shortening of solid-liquid two-phase temperature range, and refinement of microstructure.