V. V. Bukhanovsky, I. Mamuzić - The Effect of Temperature on Mechanical Characteristics of Niobium Alloys of the System Nb-W-Mo-Zr

    Data obtained for the short-term strength and ductility of thin sheet, weld metal, and welded joints of niobium alloys 5VMTs and 10VMTs of the system Nb-W-Mo-Zr in the temperature range 290 - 2 270 K are analyzed. The structure, deformation mechanisms governing plastic deformation, and the nature of alloy failure in the temperature range are determined. pdf - 331 kB

V. Sinka, L. Pešek - Growth and Damage of the a-Stabilized Layer in the Titanium Alloy VT3-1 During Thermal Cycling

    The interaction between cyclic loading and the surrounding environment has to be taken into account especially at high temperature exposure. In atmospheric conditions fatigue and oxidation take place parallel. This results in a shorter crack initiatial period and enhanced crack propagation both in thermal cycling and isothermal conditions. In the present work, the development of a-stabilized layer in an a + b titanium alloy was investigated during high temperature thermal cycling in air environment. The constrained samples were cyclically heated between the lower temperature of 200 °C and the upper limit of 900, 1000 and 1100 °C, respectively. The oxygen containing a-phase nucleated on the lamellae of the a´ martensite when during the thermal cycling the maximum temperature exceeded the transformation temperature of the alloy. Maximum temperature and total exposure time showed to be decisive for the growth of the a layer stabilized by diffusion of the oxygen into the material. In the embrittlened diffusion layer cracks were initiated, growing inward exposing new surfaces for the diffusion of oxygen and development of a-layers leading to an accelerated damage process. pdf - 201 kB

M. Kupková, M. Kupka, S. Strobl, G. Khatibi, M. Kabátová, E. Dudrová - Effective Flexural Modulus of Bars Containing Cellular-Material Layer, and the Use of this Modulus for Determining the Effective Elastic Modulus of a Cellular Material

     Rectangular bar-shaped sandwich-like samples consisting of a cellular-material core between two standard material layers were prepared. The cellular materials were made of both ferrous and bronze hollow spheres. Using these specimens and testing method based on flexural vibrations, expected differences were observed in effective modulus values determined by means of vibrations parallel and perpendicular to layers. Information on distribution of material throughout the bar cross section was obtained through metallographic studies. The thickness of particular layers, measured values of “parallel” and “perpendicular” effective flexural modulus, and expressions derived for flexural rigidity of quasi-layered bars were used for evaluating the values of effective Young’s modulus of material of particular layers constituting the sample. Reasonable agreement was found among results obtained for various samples. pdf - 166 kB

L. Cristea, R. R. Piticescu, B. Popescu, M. Teleanu - Hydrothermal Synthesis of Zirconia Nano-Powders and Films

     The synthesis of nano-powders was accomplished using different physical, mechanical and chemical methods. Hydrothermal processes have been recently reported as a very attractive route in the synthesis of both zirconia powders and films. The present paper presents some aspects of the microstructural evolution of zirconia nanomaterials obtained via hydrothermal process starting from soluble peroxide precursors. pdf - 293 kB

J. Hidvéghy, J. Micheľ, M. Buršák - Residual Stress in Microalloyed Steel Sheet

     The hot rolling sheet production technology leaves behind in the sheet residual surface stress fields, which are due to the uneven strip cooling during rolling, the process of coiling, coil cooling and cold deformation during uncoiling. What concerns cold deformation during coil straightening, we expect that after exceeding the yield point in a surface layer on the tensile strained side, compressive residual stress remains there, and on the other, compressed side tensile residual stress. The influence of surface residual stress on properties of hot rolled steel KODUR E460 TS, KODUR E550 TS and KODUR E700 TS is investigated in this work. pdf - 129 kB

J. Bilík, V. Roubíček, Š. Vilamová, P. Pustějovská - Actual Possibilities of Coal Utilization in Iron Metallurgy

     This paper deals with actual possibilities of coal utilization in iron - and steelmaking. Particular attention is devoted to coal utilization in the blast furnace process. Our paper presents also coal utilization as alternative methods of iron production. The script notices even other possibilities of coal utilization in metallurgy. Concludingly, orientation form is introduced for the further development of coal usage in iron metallurgy. pdf - 179 kB