Alloy design strategy to improve fluidity of Zr-based bulk metallic glass for near-net-shape manufacturing

Abstract

The near-net-shape manufacturing via casting has great potential to commercialize bulk metallic glasses (BMGs) for the complex-shaped structural material. However, it is difficult to cast BMGs with the excellent glass-forming ability (GFA) into the precise dimensions of complex shapes, because the slow kinetics of crystallization of the BMG is related to the high viscosity and low fluidity of the melt. In this study, to overcome this limitation, Zr-based BMG with excellent GFA, hardness, and significantly improved fluidity compared to Vitreloy 106 was systematically developed. Utilizing the ZrCuNi liquidus projection, it is possible to design BMG-forming alloy compositions with a low liquidus temperature (TL) by compositional tuning in the ZrCuNiAl quaternary alloy system. We also propose an alloy design methodology that can simultaneously improve the key properties of Zr-based BMGs by minor addition. Interestingly, Ag can be added instead of Zr in ZrCuNiAl alloys, resulting in higher hardness and lowest TL without deterioration of GFA. Thus, the addition of Ag can lead to a significant increase in flow length of about 40% compared to that of Vitreloy 106, because the TL is a dominant factor that determines fluidity under various casting conditions. This study shed light on how to simultaneously improve the dimensional accuracy of BMG products and life span of casting facilities when manufacturing through various conventional casting methods, which should be important to fabricate macro to nano-sized industrial parts through BMGs.