Three-phase strengthening and toughening mechanism of MgY12Zn2.5 magnesium alloys

Abstract

The microstructural evolution of as-cast, solid-solution-treated, extruded, and forged MgY12Zn2.5 magnesium alloys were observed, and the strengthening and toughening mechanisms of the deformed alloys were studied. The results showed that α-Mg solid solution was transformed into a lamellar structure of the 14H-LPSO + 2H-Mg phase, after solution treatment. The lamellar composite structure of the 14H-LPSO, 2H-Mg, and 18R-LPSO was formed by extrusion of the solid-solution-treated alloy and then a forging deformation. In the process of plastic deformation, the three-phase (2H-Mg, 14H-LPSO and 18R-LPSO) coordinated deformation and uniform distribution of the stress and strain, effectively restricting the stress concentration at the interface and delaying the initiation of cracks. The ultimate tensile stress (UTS), yielding tensile stress (YTS), and elongation of the MgY12Zn2.5 at room temperature were 415.0 MPa, 395.25 MPa, and 14.2%, respectively, reaching the level of the high-strength and high-toughness magnesium alloys.