Grain Growth Kinetics of Magnesium Alloys Containing Aluminum and Rare-Earth Element Gadolinium

Microstructural evolutions during the high-temperature annealing of Mg alloys containing Al and Gd and after the extrusion process were evaluated and compared to those of the AZ61 alloy. It was revealed that during exposure at the elevated temperatures, the presence of (Mg,Al)3Gd phase, in the form of fine and dispersed particles in the matrix after the extrusion process, could be favorable for the inhibition of grain growth. It was also found that the Al2Gd particles could not effectively retard the coarsening of grains. On the other hand, the grain growth of AZ61 alloy was found to be problematic, which was related to the dissolution of the Mg17Al12 intermetallic phase at temperatures higher than 300°C. In the Mg alloys containing both Al and Gd elements, the increased thermal stability was observed, which was ascribed to the rise of the melting temperature. Finally, some abnormal grain growth was observed in the presence of Al2Gd phase, which was attributed to the nonuniform pinning of grain boundaries by this intermetallic compound.