Microstructure and Mechanical Properties of a Mg94Y4Ni2 Alloy with Long Period Stacking Ordered Structure

Microstructure and mechanical properties of the Mg94Y4Ni2 alloy (at.%) during homogenization, extrusion, and aging processes were systematically investigated using x-ray diffractometer, optical microscopy, scanning electron microscopy, transmission electron microscopy, and electronic universal testing machine. The results showed that the morphology evolution of 18R LPSO structure during annealing in Mg94Y4Ni2 alloy was different from that of Mg-Y-Zn systems. The 18R-type Mg12YNi phase was thermal stable and was not transformed into 14H structure when annealed at 773 K. After solution treatment at 773 K for 10 h and aging at 498 K for 24 h (T6 treatment) of the extruded alloy, a great amount of fine beta' phases were precipitated dispersedly in the matrix. The tensile tests showed that the extruded Mg94Y4Ni2 alloy after T6 treatment exhibited good tensile properties with ultimate tensile strength of 453 MPa and elongation to failure of 2.4% at room temperature. Thus, a high-strength Mg94Y4Ni2 alloy, which is strengthened by the coexisted LPSO phases and beta' precipitates, can be prepared via simple hot extrusion and T6 treatment.