Effects of yttrium addition on thermoplastic formability of Zr-Cu-Ni-Al amorphous alloy under non-isothermal condition

Abstract

A low-cost and Be-free Zr-based amorphous system with excellent thermoplastic formability has been developed by doping a small amount of Y element. Based on the thermodynamic test data, Y addition can increase the supercooled liquid region of Zr-based amorphous alloy when it is less than 2 at%, leading to a relatively wider temperature range of thermoplastic forming. The compression experimental results reveal that (Zr0.507Cu0.28Ni0.9Al0.123)98.5Y1.5 (ZrY1.5) alloy possesses the largest Dmax value (the maximum diameter of the compressed cylindrical specimen) than other Zr-based amorphous alloys prepared in this study, thereby confirming its superior thermoplastic formability. A lower viscosity can be observed on the TMA curves of ZrY1.5 alloy, suggesting that appropriate Y addition decreases the viscous resistance of amorphous supercooled liquid. However, the more obvious deviation from Vogel–Fulcher–Tamann theoretical model indicates the weak Arrhenius temperature dependence of viscous flow behavior. The parameter ΔTTPF/D*, where ΔTTPF represents the temperature range of thermoplastic forming and D* denotes the fragility index, is found to be an effective indicator for evaluating the thermoplastic formability of the investigated Y addition Zr-based amorphous system. Finally, Zr-based amorphous nanopillar arrays have been successfully fabricated under non-isothermal condition, which further proves that Y addition Zr-based amorphous alloy is a promising candidate for nanomolding material.