Free volume formation and the high strength of pure Mg after room temperature core-sheath ECAP passes

Abstract

The present investigation is conducted to successfully deform pure Mg by equal-channel angular pressing (ECAP: channel angle 90°, corner angle 20°) using core-sheath configuration at room temperature. The microstructure of the sample after 4 passes of ECAP contained an average grain size of ∼0.3 μm and an excess free volume of ∼0.63% due to the formation of defects and dislocations during the ECAP process. The results show that local temperature increases up to 200 °C during the ECAP process causes dynamic recovery and recrystallization in the microstructure during deformation. The texture analysis shows that the first pass activates the non-basal sliding systems and the 4 passes present a relatively strong (0002) fiber texture. The highest ever reported tensile toughness of SPD processed pure Mg of about 1.784 GPa% with remarkable mechanical properties were achieved after 4 passes with an ultimate tensile strength of 223 MPa, yield stress of 170 MPa, and an elongation to failure of 8%.

Keywords

• Magnesium
• ECAP process
• Core-sheath method
• Recrystallization
• Free volume