High Mechanical Strengths of Mg–Ni–Y and Mg–Cu–Y Amorphous Alloys with Significant Supercooled Liquid Region

Abstract

Mg–Ni–Y and Mg–Cu–Y alloys were found to form an amorphous solid in wide compositional ranges of 0 to 40 at%Ni or Cu and 0 to 40%Y by the melt spinning technique. These amorphous alloys exhibit a wide supercooled liquid region before crystallization and the glass transition temperature (Tg) increases from 398 to 568 K with increasing Y content, while a minimum at about 15%Ni or Cu is seen in the change of Tg with Ni or Cu content. The temperature span ΔTx (=Tx−Tg) shows a maximum around the central composition in the range where the glass transition is observed and the largest ΔTx is 41 K for Mg50Ni30Y20 and 61 K for Mg65Cu25Y10. Furthermore, the Mg-based amorphous alloys containing above about 70%Mg have a good bending ductility and the tensile fracture strength (σf) reaches 830 MPa for Mg80Ni15Y5 and 800 MPa for Mg85Cu5Y10. The specific strength defined by the ratio of σf to density is 3.5×105 N·m/kg for both alloys which is about 2.0 times as high as the highest value for conventional Mg-based crystalline alloys. The Mg-based amorphous alloys are attractive as a new type of high-strength material with light weight.