Effect of Ca, RE elements and semi-solid processing on the microstructure and creep properties of AZ91 alloy

▶ The size of solid globular α(Mg) particles decreases in semi-solid slurries of AZ91 alloy by adding Ca and RE elements, whereas it has no considerable effect on the shape factor of the solid particles. ▶ Particle growth in semi-solid slurries of AZ91 and AZRC91 alloys takes place by Ostwald ripening mechanism. ▶ The coarsening rate of solid particles in semi-solid slurries of AZRC91 alloy is lower than that of AZ91 alloy. ▶ Creep properties of AZ91 alloy was improved by adding Ca and RE elements. The thixoformed specimens exhibit the better creep resistance than the as-cast specimens.