Influence of high-pressure torsion on microstructure, hardness and shear strength of AM60 magnesium alloy

• Published in: Materials science & engineering. A, Structural materials : properties, microstructure and processing Vol. 799; p. 140158
• Main Authors: Khaleghi, A.A., Akbaripanah, F., Sabbaghian, M., Máthis, K., Minárik, P., Veselý, J., El-Tahawy, M., Gubicza, J.
• Format: Journal Article
• Language: English
• Published: Lausanne Elsevier B.V 02-01-2021; Elsevier BV
• Subjects: AM60; Crystallography; Disks; Dislocation density; Equal channel angular pressing; Extrusion; Grain refinement; Grain size; Hardness; High-pressure torsion; Magnesium alloys; Magnesium base alloys; Mechanical properties; Microstructure; Room temperature; Shear punch test; Shear strength; Texture; AM60; Shear punch test; Hardness; Texture; Magnesium alloys; High-pressure torsion
• ISSN: 0921-5093; 1873-4936
• DOI: 10.1016/j.msea.2020.140158

The evolution of the microstructure, crystallographic texture and hardness of an AM60 magnesium alloy was studied in the center and the edge parts of disks processed by high-pressure torsion (HPT) technique at room temperature. In addition, the mechanical properties were also tested by shear punch test (SPT). The number of HPT turns varied between ½ and 10. It was found that the grain size of the initial extruded material (~16 μm) decreased to ~2 and ~0.8 μm at the disk center and edge, respectively, even after ½ turn of HPT. Ten turns of HPT resulted in further grain refinement to ~1 and ~0.23 μm at the disk center and edge, respectively. The dislocation density saturated even after ½ turn with the value of ~11 × 1014 m−2. The maximum value of the hardness was ~1300 MPa that was measured at the edge of the disk deformed for ½ turn. Despite the practically unchanged grain size and dislocation density, the hardness decreased between 3 and 10 turns which can be explained by texture softening. A good agreement was observed between the yield strength estimated as one-third of the hardness and the values calculated from the dislocation density, grain size and texture. The difference between the microstructure and hardness obtained for AM60 samples processed by HPT and equal channel angular pressing (ECAP) is discussed.
•AM60 magnesium alloy was processed by HPT at room temperature.•The minimum grain size was 0.23 μm achieved at the edge of the disk after 10 turns.•The highest hardness was 1300 MPa obtained at the disk edge processed for ½ turn.•The softening observed between 3 and 10 turns was caused by the change of the texture.•The calculated and measured yield strength values were in a reasonable agreement.