Microstructure, mechanical properties, and crystallization behavior of Zr-based bulk metallic glasses prepared under a low vacuum

Abstract

The present work is devoted to an investigation of the microstructure, deformation behavior and kinetics of crystallization of Zr-based glassy alloys produced in a low vacuum environment. The data obtained indicate that small additions of rare earth (RE) metals, such as Dy, Gd, Er, to a Zr62.5Cu22.5Fe5Al10 alloy are likely to suppress heterogeneous nucleation of impurities, and thus, increase the glass forming ability (GFA), which allows obtaining glassy ingots up to 5 mm diameter even under a low vacuum. The structure of the alloys consisted of a glassy matrix and a small fraction of RE oxides. The large difference between the enthalpies of the oxide formation of copper and RE elements is responsible for the reduction of copper concentration in the regions near the oxides. According to the kinetics parameters of crystallization, the highest thermal stability observed in a Gd-bearing alloy corresponds to its good GFA. The maximum compression strength was achieved in the alloy containing 0.5 at.% of Dy. At the same time, the optimal combination of strength and plasticity, with the fracture strength of 1890 MPa and the plastic deformation of 3.3%, was observed in the alloy containing 1 at.% of Gd. A finite element modeling (FEM) analysis showed that equiaxed oxide particles can prevent propagation of a single shear band and promote generation of multiple shear bands.