Influence of Rare Earth Elements on Microstructure and Mechanical Properties of Mg_(97)Zn_1Y_1RE_1 Alloys

摘要

Mg_(97)Zn_1Y_1RE_1 (RE = La, Ce, Nd and Sm, at. %) alloys were prepared by high-frequency induction melting in an Ar atmosphere. Rods were extruded at 623 K and a ram speed of 2.5 mm · s~(-1) using a circular die with an extrusion ratio of 10. The microstructure and mechanical properties of the extruded alloys were investigated. The Mg_(97)Zn_1Y_1Nd_1 and Mg_(97)Zn_1Y_1Sm_1, alloys consisted of only two phases: α-Mg and a Mg-RE intermetallic compound. The Mg_(97)Zn_1Y_1La_1 and Mg_(97)Zn_1Y_1Ce_1, alloys consisted of three phases: α-Mg, a Mg-RE intermetallic compound, and a Mg_(12)ZnY phase with a long-period stacking ordered (LPSO) phase. Additionally, after extrusion, the three-phase Mg_(97)Zn_1Y_1RE_1, alloys, i.e., those with an LPSO phase, had a stratified microstructure and exhibited better mechanical properties than those without an LPSO. At room temperature, the yield strength and ultimate tensile strength of the three-phase Mg_(97)Zn_1Y_1La_1, and Mg_(97)Zn_1Y_1Ce_1, alloys were 381-384 MPa and 427-429 MPa, respectively, and yield strengths greater than 280 MPa were observed at the elevated temperature of 523 K.