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Použití odlitků z hořčíkových slitin
Pernica, Vítězslav ; Liškutín, Petr (oponent) ; Roučka, Jaromír (vedoucí práce)
Slitiny hořčíku mají pro své vlastnosti stále nevyužitý potenciál v technických aplikacích. Historie kovu není dlouhá, první aplikace jeho slitin začaly na začátku 20. století. Hořčík má tu vlastnost, že je velmi lehký. Váží o třetinu méně než hliník a je třetím nejužívanějším konstrukčním kovem. Problematická je však jeho příprava a zpracování, jelikož má hořčík vysokou afinitu ke kyslíku. To se projevuje intenzívním hořením. Během století vývoje se zdokonalila jak výroba, tak slitiny. Využití slitin hořčíku nabylo většího významu a nejvíce se uplatňuje zatím v automobilovém průmyslu. V poslední době expanduje poptávka nejvíce v elektrotechnice. Další využití lze najít v letectví, energetice, armádě a mnoho dalších odvětví.
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Determination of mechanical properties of light alloys and composites by means of Small Punch Testing
Bártková, Denisa ; Langer, J. ; Dymáček, Petr ; Válka, L.
Nowadays, in many testing areas a volume of experimental material is limited (laboratory-scaled volume, semidestructive approach). Therefore many testing techniques on miniature samples were devised. Principle of Small Punch Test (SPT) method is a penetration of small puncher through thin disc placed on a ring until the disc bursts. In dependence on loading mode it can provide information comparable to uniaxial tensile tests (UTT) and/or conventional constant load creep tests. However clarification of relations between SPT and conventional methods is difficult and empirical formulas are non-universal. The aim of this study is to i) evaluate mechanical properties of aluminium and magnesium alloys and its composites by means of SPT, ii) compare SPT results with UTT, iii) validate correlation formulas from literature, iv) propose more advanced approach to define correlation between UTT and SPT. Measurement were carried out at constant deflection rate (SPT-CDR) in two different laboratoires. Results from both laboratories were compared to evaluate the reproducibility of the method. Better results agreement was reached for the ultimate strength measurements. Yield strength results exhibited greater variance. An influence of pre-deformation of the sample on yield strength and deflection at maximum force was also identified. We can conclude, that for quantitative estimation of strength parameters we can use correlation formulas based on materials with similar composition and fracture behaviour.
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HYDROGEN STORAGE IN Mg-In-C ALLOYS: EFFECT OF COMPOSITION AND AGEING
Čermák, Jiří ; Král, Lubomír
Hydrogen storage in two Mg-In-C alloys with different In concentration, c In , was studied in the temperature range from 250°C to 350°C after five-years-ageing at room temperature. The both alloys show acceptable cycling stability, however, the storage capacity of the alloys decreased from about 5 wt. % H2 to about 2,5 and 3.1 wt. % H 2 by higher c In and lower c In , respectively after 5 years. The sorption kinetics degraded much more by high c In than by c In . PCT isotherms, TPS and DSC patterns were measured for both materials. It was found that the hydrides responsible for hydrogen storage in alloy with higher c In are slightly more stable.
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