Experimental Investigation of the Mechanical Behaviour of AZ31B Magnesium Alloy at Elevated Temperatures

Abstract—Magnesium alloy AZ31B, due to its low density and high specific strength, is widely used in aerospace and automotive applications where weight reduction is critical, and its performance at elevated temperatures is crucial for ensuring structural reliability. The mechanical behaviour of the magnesium alloy AZ31B was experimentally characterized at a constant strain rate (SR) (10–1 s–1) at temperatures from 25 to 300°C. The yield strength decreased from 201 to 75 MPa, the ultimate tensile strength decreased from 256 to 104 MPa, the modulus of elasticity decreased from 43.80 to 17 GPa, and the elongation increased from 22.5 to 71.0% as the temperature was increased from 25°C to 300°C. Field Emission Scanning Electron Microscopy (FE-SEM) fractography revealed cleavage fracture, river patterns, and a few shallow dimples in specimens tested at room temperature and a blend of cleavage patterns and shallow dimples in specimens tested at 100°C. Fractured samples revealed recrystallized coarse and fine grains with the average grain size below 10 μm, suggesting superplastic flow. The reduction factors for modulus of elasticity, yield strength, and ultimate tensile strength were also calculated in this study. The reduction factors identified in this study filled a research gap on the high-temperature mechanical properties of AZ31B magnesium alloy. The FE-SEM observations reveal underlying mechanisms such as particle-induced crack formation and brittle, sheet-like fragmentation. These findings confirm that the fracture behaviour of AZ31B is highly influenced by elevated temperatures and microstructural inhomogeneities, which affect the overall ductility and failure mode of the material.