Improved Tensile Ductility by Severe Plastic Deformation for Nano-Structured Metallic Glass

The Influence of High-Pressure Torsion on the Free Volume and Shear-Band Formation during the Indentation of Vit105 Metallic Glass

The research on structural features, microhardness distribution, and deformation features of Vit105 bulk metallic glass (BMG) before and after high-pressure torsion (HPT), as well as after relaxing annealing, has been carried out. HPT n = 1 leads to an increase in free volume ΔV, and relaxing annealing leads to a decrease in ΔV and non-uniformity relative to the initial state of BMG. In the initial BMG and in the BMG after relaxing annealing, microhardness is uniformly distributed over the surface, while in the material subjected to HPT, the microhardness distribution is more heterogeneous. The bonded-interface indentation of the BMG has been conducted in different states. The formation of numerous concentric bands around the indenter is observed. The pattern of band distribution is more homogenous in Vit105 BMG alloy before HPT. In relaxed samples, the bands often have fractures and irregularities, as well as cracks that can be seen under the indents. After HPT, the formation of several intensity bands can be observed, as well as a number of low-intensity ones between the main intensity bands. The average distance between the bands in the initial BMG and BMG after HPT is close to identical, while the distance between the bands is smaller in the relaxed state, which reflects the lower plasticity of the material after annealing.

Influence of High-Pressure Torsion and Accumulative High-Pressure Torsion on Microstructure and Properties of Zr-Based Bulk Metallic Glass Vit105

Vit105 (Zr52.5Cu17.9Ni14.6Al10Ti5 at. %) bulk metallic glass samples were processed by high-pressure torsion and accumulative high-pressure torsion. By DSC, XRD and SANS methods it was shown that accumulative high-pressure torsion allows for achieving high real strains and leads to an increase in the free volume and significant transformation of the structure. Minor crystallization was detected after high-pressure torsion processing.

A Multiple Twin-Roller Casting Technique for Producing Metallic Glass and Metallic Glass Composite Strips

To date it has not been possible to produce metallic glass strips with a thickness larger than 150 μm via single-roller melt spinning technique, and it remains challenging to produce thick metallic glass strips. In this work, a multiple twin-roller casting technique is proposed for producing thick metallic glass and metallic glass composite strips. A triple twin-roller casting device, as a specific case of the multiple twin-roller, was designed and manufactured. The triple twin-roller device possesses a high cooling rate and involves a long contact time between the melt and the strip, which makes it an efficient technique for producing metallic glass strips that avoids crystallization, although the solidification temperature ranges of metallic glasses are as wide as several hundred Kelvins. The two prepared metallic glass (MG) strips are in a fully amorphous state, and the MG strip shows excellent capacity of stored elastic energy under 3-point bending. Furthermore, the Ti-based metallic glass composite strip produced via the triple twin-roller casting exhibits a novel microstructure with much finer and more homogenously orientated β-Ti crystals, as compared with the microstructure of metallic glass composites produced by the common copper mold casting technique.