Modeling of extremely ductile behavior of Zr-based bulk metallic glasses under compressive strain paths for solid-state processing

In addition to extremely high strength, manufacturing temperatures of bulk metallic glasses (BMGs) relative to steels are low making them to desired energy saving engineering materials. However, BMGs are significantly brittle at low temperatures. To further increase suitability of BMGs for widespread use, it is essential to understand their plastic deformability (ductility) for high-tech solid-state processes at lowered temperatures. In this work, extremely large deformation behavior (near 80% in compression) of industrially important Zr-based BMGs was investigated. The experimentally measured results aided in the development of an appropriate constitutive model and revealed the micromechanisms affecting the characteristic macroscopic deformation behavior including softening and hardening. The measured and model results showed that the ductility can be significantly improved through chemical composition changes, such as a reduction in the Cu content and an increase in the Zr, Ti, or Be contents. In contrast to previously announced conclusions on the high glass-forming ability (GFA) being the precursors to ductility, formation of sufficiently low degree of crystallization during cooling improved ductility of as-cast specimens under loadings. These observed properties are important in assessing the ability of BMGs for solid-state processing.