Development of High Strength and Toughness Magnesium Alloy by Grain Boundary Control

The mechanical properties, such as strength and fracture toughness, were investigated using caliber rolled Mg-6wt.% Al-1wt.% Zn (AZ61) alloy, which is the material consists of a constrained plane other than the rolling direction plane and is compressed non-simultaneously from two directions. The initial microstructural observations showed that the caliber rolled AZ61 alloy had a high fraction of low-angle grain boundaries and an average grain size of 2.2 mu m. In addition, particles with an average size of 100 nm existed in the matrix. This alloy showed a yield strength of 423 MPa and a fracture toughness of 34.1 MPam(1/2). A combination of grain refinement, formation of low-angle grain boundaries and dispersion of fine particles is one of the effective microstructural controls to produce the magnesium alloys with fracture toughness similar to the conventional high strength aluminum alloys.