|
| |
|
|
Phase transformations in Mg-Zn-based alloys
Fischer, Josef ; Stulíková, Ivana (advisor) ; Kekule, Tomáš (referee)
In this thesis MgZnAlCa and MgZnAl materials were studied. For the study of phase transitions on studied materials the method of measuring the changes of resistivity and hardness was used. The measures were carried out at the temperature of 77 K and at the room temperature. Chosen annealing regimes were 20 K / 20 min and also regime without temperature change - 300 řC. Courses of annealing curves are similar. Material MgZnAlCa shows simpler course of annealing curves than material MgZnAl. With both materials the icosahedral quasicrystalis phase was observed. V této práci byly zkoumány materiály MgZnAlCa a MgZnAl. Pro studium fázových změn ve studovaných materiálech byla použita metoda měření změn rezistivity a tvrdosti. Měření probíhala při teplotě 77 K a při pokojové teplotě. Zvolené žíhací režimy byly 20 K / 20 min a dále režim bez změny teploty - 300 řC. Průběhy žíhacích křivek jsou podobné. Materiál MgZnAlCa vykazuje jednodušší průběh žíhacích křivek než materiál MgZnAl. V obou materiálech byla pozorována icosahedrální kvazikrystalická fáze.
|
|
|
Effect of production method on properties of light structural alloys
Hylský, Josef ; Stulíková, Ivana (advisor) ; Vlach, Martin (referee)
A difference in phase transformations in the Mg-Y-Nd-Sc-Mn alloy prepared by two different methods - squeeze casting and powder metallurgy - was studied by relative resistivity changes and hardness measurements. The measurements took place at 77K and at room temperature in the isochronal annealing procedure of 30 řC / 30 min in temperature range of 90 řC - 510 řC. Results achieved in the squeeze cast alloy are in agreement with results of parallel research of microstructure, which proved the existence of thin hexagonal plates up to 390 řC, which are parallel to matrix basal planes. Prismatic plates of the stable phase Mg5(NdxY1-x) developed during annealing melt into solid solution above 390 řC, while particles of the Mn2Sc phase pass even annealing at 510 řC and only coarsen. Previous heating at high temperatures, when solid solution is enriched by Y and Nd atoms, stress precipitation processes, which correspond to precipitation sequence of the Mg-Y-Nd system with two metastable phases and one Mg5(NdxY1-x) equilibrium phase. Only indistinctive resistivity and hardness changes caused by dissolution of thin basal hexagonal plates and by a development of temperature stable Mn2Sc particles are observed during annealing up to 420 řC of the material prepared by powder metallurgy. A dissolution of the equilibrium...
|
|
| |
|
| |
guest ::
