Ultrahigh strength as-extruded Mg-10.3Zn-6.4Y-0.4Zr-0.5Ca alloy containing W phase

A new ultrahigh-strength W phase (Mg3Y2Zn3) containing Mg-10.3Zn-6.4Y-0.4Zr-0.5Ca (wt.%) alloy with medium RE content has been fabricated through conventional casting and indirect extrusion. The as-extruded alloy exhibits ultimate tensile strength of 466 MPa, tensile yield stress of 447 MPa and elongation to failure of 4.7%. The as-cast Mg-10.3Zn-6.4Y-0AZr-0.5Ca (wt.%) alloy is mainly composed of alpha-Mg and lamellar eutectic alpha-Mg and W phase distributed at grain boundaries. After extrusion, the coarse lamellar W phases in the as-cast alloy are broken into fine particles of about 0.5 mu m, dispersing in the particle bands along the extrusion direction. The as -extruded alloy exhibits a bimodal microstructure consisting of ultrafine dynamic recrystallized (DRXed) grains with fine broken W phase particles at the DRXed grain boundaries and coarse un-DRXed regions. Large number of nano W phase and small amount of nano beta(2)' phase are dynamically precipitated in the coarse unDRXed regions during extrusion, which contribute to the ultrahigh strength of the as-extruded alloy. (C) 2016 Elsevier Ltd. All rights reserved.