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The pseudoelasticity and the shape memory effect in CoNiAl alloys
Kopeček, Jaromír ; Jarošová, Markéta ; Jurek, Karel ; Heczko, Oleg
The cobalt alloys (close to the CoNiAl stoichiometry) are the less known shape memory alloys. Such behavior is consequence of the martensitic transformation. The pseudoelasticity is caused by the stress-induced martensitic transformation above the equilibrium martensite start temperature from high temperature cubic phase (austenite) to lower symmetry phase(martensite). In CoNiAl the pseudoelastic behavior can be obtained by the high temperature annealing. In presented work the effect of the annealing temperature on both pseudoelastic behavior and microstructure was investigated.
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Effect of chemical composition on the hot deformation behavior of selected iron aluminides
Šumšal, V. ; Schindler, I. ; Kopeček, Jaromír ; Šíma, V.
The influence of chemical composition on the deformation resistance of iron aluminides was studied by the plastometric tests on three types of Fe – 40 at. % Al based materialsalloys; especially the influence of zirconium and boron, respectively effect of fine TiB2 particles addition was investigated. All materials were prepared using the identical procedure. The samples were pre-heated to a temperature of 1200 °C and then deformed at temperatures from 800 to 1200 °C, the nominal strain rate was 0.05 s-1, 0.4 s-1-1, 4 s-1 and 30 s-1. The relationship describing the maximum deformation resistance of aluminides depending on the temperature-compensated strain rate was derived from obtained data. The values of activation energy and hot deformation resistance of the studied materials were compared and the differences interpreted in terms of physical-metallurgical effects of additives.
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Detection of Elliptical Particles in Atomic Force Microscopy Images
Sedlář, Jiří ; Zitová, Barbara ; Kopeček, Jaromír ; Todorciuc, T. ; Kratochvílová, Irena
In this paper we describe a method for detection and measurement of elliptical particles in atomic force microscopy (AFM) images. AFM imaging is used in physics to scan surfaces; the measured heights are represented by pixel values. Each sample in our project consisted of elliptical particles of principally the same size; the size could be characterized by the average length and width of a number of salient particles. The method we proposed is based on segmentation of undamaged particles and their approximation by ellipses; the major and minor axes provide robust estimates of the lengths and widths of the particles, respectively. The method is robust to distortions typical of AFM images. Its performance was demonstrated on images of pyrroles and compared with manual detection. Results show that the automatic method could be used in place of the time-consuming manual detection.
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