Study On The Metamorphism Of Ce And Sb To AZ91 Magnesium Alloy As-cast And Semi-solid Microstructure

In this paper.the most popular AZ91 magnesium alloy was studied.and the alloy was modified after adding different quantity of Ce ,Sb and (Ce +Sb) to it, the influence of three kinds of modificators to the as-cast and semi-solid microstructure of AZ91 magnesium alloy was analysed by the metallography microscope,SEM ,XRD and graphical analysis softwares ,etc. The results indicate that:Both Ce and Sb have the function of refining the casting grain of AZ91 magnesium alloy. After adding the modificators to magnesium alloy, α-Mg grains and secondary dendrites are refined. When adding 1.2%Ce,0.8%Sb and 0.6%(Ce+Sb),the metamorphic results are the best ;Not only the primary crystal has been modified obviously.but also the eutectic structure has been modified greatly. With the increase of the addition.the precipitation mount of eutectic microstructure decreased,reticular structure disrupted to paticals and the mount increased.The microstructure of semi-solid is influenced greatly by different as-cast structures , the finer the brilliant is the finer the semi-solid is. The semi-solid of modified AZ91 alloy by adding Ce and/or Sb have been refined.when adding(Ce +Sb), the metamorphic result is the best,the spheric grains of semi-solid refined from 119μm to 55μm and the solid rate reduced from 69.6% to 53.1%.After adding Ce and Sb,the phases of Al₁₀Ce₂Mn₇ and Mg₃Sb₂ have been produced in the structure of AZ91 magnesium alloy with the forms of the pole and bulk and diepersed in it.These two kinds of phases hinder the growth of α-Mg brilliant and eutectic structure while the alloy solidifies, have certain function of the refinement to the grain.