Microstructure and mechanical properties of LPSO dominant Mg-2Y-Cu-TM (TM=Cu, Zn, Co, Ni) alloys

Abstract

The microstructures and mechanical properties of Mg 96 Y 2 Cu 2 , Mg 96 Y 2 Cu 1 Zn 1 , Mg 96 Y 2 Cu 1 Co 1 and Mg 96 Y 2 Cu 1 Ni 1 (at.%) alloys were investigated. The α-Mg matrix, the long-period stacking order (LPSO) phases and intermetallic compounds were contained in the as-cast Mg-2Y-Cu-TM (TM = Cu, Zn, Co, Ni) alloys. The addition of Co leads to a large number of compounds in the alloy resulting in the poor performance on mechanical properties. On the contrary, the supplement of Ni increased the content of LPSO phases, which was beneficial to improvement of mechanical properties. Tensile tests revealed the tensile yield strength (TYS), ultimate tensile strength (UTS) and elongation of the extruded Mg 96 Y 2 Cu 1 Ni 1 were 371 MPa, 439 MPa and 6.9%, respectively. The specific pin-stripe like LPSO phases observed in Mg 96 Y 2 Cu 2 and Mg 96 Y 2 Cu 1 Ni 1 significantly improve the mechanical properties. The LPSO volume fraction and morphologies instead of grain size are the main factors affecting the mechanical properties in this study. The notion, dispersion of LPSO phases, can be used to describe the well-aligned LPSO phases in horizontal direction, which effectively strengthens the extruded alloys; it can be calculated by the formula. • The LPSO dominant Mg-2Y-Cu-TM (TM = Cu, Zn, Co, Ni) alloys were systematically investigated. • The notion, dispersion of LPSO phases, can be used to describe the well-aligned LPSO phases in horizontal direction; it can be calculated by the formula: D = ∑ N ∑ L . • The Mg 96 Y 2 Cu 1 Ni 1 alloy with the highest value of dispersion exhibits the best mechanical properties. • The thin pin-stripe-like LPSO phases in the Mg 96 Y 2 Cu 2 and Mg 96 Y 2 Cu 1 Ni 1 alloys had a positive effects on magnesium alloy mechanical properties.