Effects of calcium and rare earth elements on microstructure and creep properties of AZ91 alloy in as cast and semisolid processed conditions.

<title/> The effect of Ca and rare earth (RE) elements on the microstructure and creep properties of AZ91 magnesium alloy was studied in as cast and semisolid processed conditions. The results showed that in as cast condition of AZ91 alloy grain refinement takes place and the amount of β-Mg17Al12 intermetallic phase decreases due to addition of Ca and RE elements. Also, two new Al11RE3 and Al2Ca intermetallic compounds are formed in the Ca and RE containing alloy. In the semisolid microstructure, the size and shape factor of the primary globular α-Mg phase and the size of the α-Mg grains formed during secondary solidification decrease by adding Ca and RE elements into AZ91 alloy. It was also shown that the creep properties of AZ91 alloy is greatly improved by adding Ca and RE elements in the as cast and semisolid processed specimens. [ABSTRACT FROM AUTHOR]