Papers by Author: Vladimir Z. Bengus

Abstract: The investigations of the failure characteristics of Fe76Ni2Si9B13 bulk amorphous alloys prepared by shock wave consolidation of powders were performed. The strength decreased with the lowering temperature from 300 to 4.2 K. For this temperature interval, the brittle failure prevails. The failure propagates across particles as well as along particle boundaries. The riverlike pattern with fine dimples was observed on the fracture surface. The apparent surface energy and the fracture toughness values estimated by means of the fractography were similar to these for typical brittle materials.

Abstract: The fracture surface morphology of Fe76Ni2Si9B13 bulk amorphous alloys failed in compression at temperatures from 4.2 to 300 K was investigated. The samples were prepared by the explosive compaction technique from amorphous powder. It has been found that fracture stress decreases with temperature from 300 to 4.2 K. In this temperature range, the brittle failure prevails. The failure propagates across particles and along particle boundaries too. The fracture micromorphology is riverlike pattern with fine dimples.

Abstract: Plasticity of ultra-fine grained (UFG) zirconium (grain size ~ 0.4 µm), produced by intensive plastic deformation (IPD) - a combination of extrusion, annealing, and drawing, have been studied within the temperature range 300 – 4.2 K in uniaxial compression. It was found that decrease of grain sizes in the result of IPD leads to considerable increase of strength characteristics for the UFG zirconium in comparison with coarse-grained (CG) zirconium (in 6 times at 300 K and 4 times at 77 K); and plasticity of the UFG zirconium keeps rather large (strain > 0.15). Two stages of the strain-hardening and decrease of the activation volume for plastic flow with deformation have been registered. A conclusion was made about the identity of basic deformation mechanisms in the UFG and CG zirconium: simultaneous action and mutual influence of intragrain dislocation gliding and twinning.

Abstract: Low temperature mechanical characteristics under quasistatic uniaxial tension and compression have been studied of ultra fine-grained structural state of polycrystalline titanium – nanostructured titanium, processed by the equal channel angular pressing (ECAP). Values of the yield stress and the uniform plasticity at 300, 77, and 4.2 K for nanostructured (NS) and polycrystalline coarse-grained (CG) titanium of different commercial purity have been compared.