Evolution of microstructure and hardness in an AZ80 magnesium alloy processed by high-pressure torsion

An AZ80 magnesium alloy with an initial grain size of ∼25 μm and a hardness of Hv ≈ 63 was processed by high-pressure torsion (HPT) at room temperature for up to 10 turns under an imposed pressure of 6.0 GPa. After processing, the specimens were examined by optical microscopy and transmission electron microscopy and measurements were taken of the Vickers microhardness along diameters of the HPT discs. The results show that the grains are refined to ∼200 nm after 5 and 10 turns of HPT and the hardness increases to Hv ≈ 120 at an equivalent strain of ∼30. There is a saturation condition and no further hardening at additional equivalent strains up to >200.