Consolidation of the Amorphous Zr₅₀Cu₅₀ Ribbons by High‐Pressure Torsion

Abstract

High-pressure torsion is used to consolidate the melt-spun Cu 50 Zr 50 amorphous ribbons. The high-pressure torsion processing is conducted varying the strain using different numbers of anvil rotations. Optical microscopy (OM) and transmission electron microscopy (TEM), X-ray diffraction (XRD) are used to study the effect of processing regimes on consolidation and structural changes. Oxide layers, which are present on the surface of the initial amorphous ribbons, hinder the consolidation of ribbons into fully dense samples. Individual ribbons are clearly observed in the central region of the specimen deformed for one rotation, whereas the edge regions look more consolidated due to the strain gradient along the radius during processing. An increase in strain (by increasing the number of rotations) improves the homogeneity of the consolidated samples. The high-pressure torsion processing for ten rotations leads to the formation of dense samples with a minor concentration of small crack-like defects in the central region. Apparently, the oxides become refined and are distributed in the matrix predominantly in the form of fine particles. Possibly, there is also some dissolution of surface oxides with the formation of a solid solution of oxygen in the amorphous metallic matrix. Amorphous Cu-Zr ribbons are known from the early 1980s. [1] Interest in the study of this system was also caused by the discovery of Cu-Zr in form of bulk metallic glasses (BMGs). [2-5] Cu-Zr BMGs and multicomponent BMGs based on Cu-Zr with minor additions of Al, Ag, Hf, and Zn or rare earth elements arouse a great scientific interest due to their high yield strength, large elastic strain limits, large compressive plasticity, and high corrosion resistance, which make them promising candidates for widespread structural applications. [6-12] Despite a high glass-forming ability of multicomponent BMGs based on Cu-Zr, Cu x Zr 1Àx binary alloy can be cast into fully glassy rods with a diameter of not more than 2 mm. [4] It is easier to produce a homogeneous amorphous state in the Zr 50 Cu 50 alloy by melt spinning, resulting in thin ribbons. Methods of consolidation can be used to overcome this limitation.