National Repository of Grey Literature 17 records found  1 - 10next  jump to record: Search took 0.01 seconds. 
Study of advanced high strength magnesium alloys by in situ techniques
Fekete, Klaudia ; Dobroň, Patrik (advisor) ; Lejček, Pavel (referee) ; Mayama, Tsuyoshi (referee)
The aim of the present doctoral thesis was to reveal the active deformation mechanisms in novel high strength magnesium (Mg) alloys using advanced in-situ techniques with high time and space resolutions. The deformation behavior of two extruded Mg-LPSO alloys with a different volume fraction of the long-period stacking ordered (LPSO) phase was investigated in tension and compression at room temperature and in compression at 200 řC, 300 řC, and 350 řC. In order to support the results obtained by in-situ acoustic emission and synchrotron diffraction methods, detailed microstructure investigation was provided by transmission and scanning electron microscopy, particularly the backscattered electron imaging and electron backscatter diffraction technique were used. The results indicate that both temperature and the LPSO phase content significantly influence the plasticity of the magnesium matrix, particularly they affect the activation of extension twins and non-basal slip. Moreover, both parameters have a high impact on the formation of the deformation kinks in the LPSO phase. Keywords: Mg-LPSO alloys, deformation mechanisms, acoustic emission, synchrotron diffraction, in-situ methods.
3D characterization of material structure using scanning electron microscopy (SEM) and focused ion beam (FIB)
Hradilová, Monika ; Jäger, Aleš ; Lejček, Pavel
The possibilities of analysis can be enhanced by utilizing focused ion beam (FIB). The FIB instrument allows revealing the structure in the third dimension by controlled and precise milling of the material. In combination with electron beam and suitable detector is possible to describe crystallography (EBSD) or chemical composition (EDS) etc. in three dimensions (3D). Thus, it is feasible to define real size, shape and distribution of microstructure features such as grains, grain boundaries, phases, precipitates and micropores.
Structure and properties of ultrafine-grained aluminium alloys prepared by severe plastic deformation (ECAP)
Dám, Karel ; Jäger, Aleš ; Lejček, Pavel
The aim of this work is to find the dependence between Equal-Channel Angular Pressing (ECAP) processing conditions and final microstructure of aluminium alloys based on Al-Mg-Sc.
New models in grain boundary engineering of iron and ferritic steels
Lejček, Pavel ; Šedá, P. ; Kinoshita, Y. ; Jäger, Aleš ; Yardley, V. ; Tsurekawa, S.
Model experiments with growth and annealing of a tricrystal of an Fe-3mass%Si alloy are reported which display inclinations of the grain boundaries to establish low energy orientations.
Microstructure and texture evolution during ecap processing of pure magnesium
Šedá, P. ; Jäger, Aleš ; Lejček, Pavel
The aim of the present work is to outline the microstructure and texture evolution of pure magnesium during severe plastic deformation by ECAP. A suitable temperature for ECAP processing is also discussed.
Směrová krystalizace eutektika Ti-Al-Si
Vojtěch, D. ; Lejček, Pavel ; Kopeček, Jaromír ; Bialasová, K.
Results of directional solidification experiments with eutectic alloys composed of matrix and silicide particles. It is shown that the matrix is more affected by directional solidification than silicides.
Problémy krystalizace slitin na bázi B2-FeAl
Kopeček, Jaromír ; Jurek, Karel ; Šíma, Vladimír ; Lejček, Pavel
Although the main source of the grain boundary weakness in FeAl arises from environmental embrittlement, important source seems to be of the intrinsic nature. The single crystals prepared by Bridgman method contain the star cracks when grown with growth rates higher than 9 mm/h. At lower growth rates the stress induced by solidification is not high enough to cause crack initiation.
Lomové chování polykrystalické slitiny Fe-2,3%V legované fosforem
Lejček, Pavel ; Pokluda, J. ; Šandera, P. ; Horníková, J. ; Vlach, B. ; Jenko, M.
Fracture behavior of a polycrystalline Fe-2.3%V alloy doped by 0.12% phosphorus show that the mode of the fracture depends on grain boundary segregation of phosphorus intergranular fracture runs along grain boundaries containing more than about 17at.% of segregated phosphorus.
Odbočení trhliny (110)[001] v krystalech alfa-železa zatížených v módu I
Prahl, Jakub ; Machová, Anna ; Karlík, M. ; Landa, Michal ; Haušild, P. ; Sedlák, Petr ; Lejček, Pavel
The work is devoted to experimental and theoretical studies of the brittle-ductile behavior at the crack front of the crack (110)[001] that in fracture experiments deviated under angle 45 degrees with respect of the original direction of the potential crack extension. In the framework of experiments, beside the fracture tests, also scanninc electron microscopy and acoustic emission detection were performed. Theoretical studies are based on 3D atomistic simulations by molecular dynamic technique at room temperature.

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