Unraveling the role of relaxation and rejuvenation on the structure and deformation behavior of the Zr-based bulk metallic glass Vit105

Abstract

The influence of relaxation and rejuvenation on the deformation behavior of the Zr-based bulk metallic glass Vit105 (Zr52.5Cu17.9Ni14.6Al10Ti5) was investigated, where a well-defined thermal history was systematically introduced by thermal treatments. Samples with a progressively lower fictive temperature exhibit a lower enthalpic state, coupled with a reduced degree of free volume, which is responsible for a continuous embrittlement observed in three-point beam bending tests. The generated database allows an assessment of the mechanical behavior of any amorphous component made of Vit105 by simple calorimetric measurements and the determination of the fictive temperature, which is of special interest for complex parts that cannot be easily evaluated in mechanical tests. Diffraction experiments with high energy synchrotron X-ray radiation reveal a correlation between the increase in rigid 3-atom cluster connections with the reduction in the fracture strain, as a measure of ductility, indicating a strong correlation with the thermal history. While the atomic connections seem to have a crucial contribution to the ductility, changes of the short- and medium-range order seem to be equally important. The current findings provide fundamental insights into the role of thermal history in metallic glass forming alloy systems and how it can be used to manipulate the structure and tailor their mechanical properties specifically to the needs of each application.