Effects Of Ce, Ca And Electromagnetic Stirring On Microstructure And Mechanical Properties Of AZ91 Magnesium Alloy

Compared with other structural materials, magnesium alloys have many excellent properties, but the poor mechanical properties limit their wide use. With wider and wider applications of magnesium alloys in the automobile and IT industries, the producers all over the world have pay much attention to the researches and applications of the magnesium alloys. It is proved that the refining grain can improve mechanical properties of materials, so it is very important to find an effective grain refiner and technique for magnesium alloys.In this paper, the grain refiner and technique for the AZ91 magnesium alloys are studied by observing their metallurgical structures at as-cast and heat treatment condition. The research methods conducted are adding Ce or Ca to the AZ91 alloy respectively and applying the electromagnetic field on the AZ91 or AZ91 + 0.8%Ce. The results show that Ce and Ca can remarkably refine the grain size of AZ91 magnesium alloy. The optimum content of Ce% and Ca% is 0.8% 0.1% respectively, and the grain size can be reduced 58% 43.7%. As expected, electromagnetic stirring can refine structure of α-Mg phase and lead to action of spheroidization. Compared with the AZ91 alloy, however, spheroidization in the AZ91 + 0.8% Ce alloy is poor, and a new needle-shaped phase precipitate. As the stirring voltage increases, the a-Mg phase size of the AZ91 and AZ91+0.8% is reduced 52.6% and 41%. The optimum voltage range is 75-125 voltage. At last, the mechanical properties of the AZ91 alloy are tested, which proves that mechanical properties of the AZ91 alloy are improved due to grain refinement.