The aim of the paper is to determine the influence of hot deformation conditions on σ-ε curves and microstructure evolution of new-developed high-manganese C-Mn-Si-Al-Nb austenitic steel. The force-energetic parameters of hot-working were determined in continuous and multi-stage compression tests performed in a temperature range of 850 to 1100°C by the use of the Gleeble 3800 thermomechanical simulator. Evaluation of processes controlling work-hardening were identified by microstructure observations of the specimens water-quenched after various conditions of plastic deformation. Multi-stage compression tests with true strain of 0.29 permit to use the dynamic and metadynamic recrystallization for forming the fine-grained, austenite microstructure of steel in the whole range of deformation temperature.

Light alloys like aluminum and its alloys have excellent physical and mechanical properties for a number of applications. The use of aluminum alloys can significantly decrease the mass of automobiles without decreasing structural strength. Therefore, the reason of this work was to determine the optimal cooling rate values, to achieve good mechanical properties for protection of this aluminum cast alloy from losing their work stability, and to make it more resistant to action in hard working conditions. The carried out investigations have allow to found that changes in the cooling rate do not cause changes in the phase composition, revealing the Al 2 Cu and Al 5 FeSi phase especially, but only changes the morphology of a ? b eutectic as well as the particle size and secondary dendrite arm spacing. As a result, the number of fine crystals in per unit volume increases, leading to a fine grain structure, which influences the recalescence temperature. The purpose of this research work is to investigate the thermoderivative interdependencies occurred in analyzed aluminum cast alloys using Universal Metallurgical Simulator and Analyzer. For the investigation, the cast AlSi9Cu aluminum alloy was used. As a result of this research, the cooling rate influence on the structure and mechanical properties changes was investigated. The cooling rate was set in a variable range of 0.16-1.25°C s -1 , where the cooling rate of 0.16°C s -1 corresponds to freely cooling, without any forced air flow.

In this study, the change of the cooling rate in the range of about 0.1-1°C s -1 and the addition of Sr on the crystallization kinetics of the cast zinc alloys of the ZnAlCu type, as well as its relation to the microstructure were also investigated. Therefore, the aim of the rapid crystallisation is the achievement of materials with better properties, which can be obtained by refinement of the dendritic or eutectic microstructure, elimination of segregation, or creation of metastable phases and their morphology changes. In the investigated alloys, the change of cooling rate of 1°C s -1 has caused microstructure's refinement as well as increase in hardness. Increase in the cooling rate causes also morphology changes of the g ? a eutectic, and makes generally a global overcooling of the alloy as well as change in the temperatures at the beginning of crystallization T DN and of the alloy crystallization T S . The presented investigations concerning the electron microscopy methods, including transmission electron microscopy, allow revealing the crystallographic structure, based on the d-spacing changes, as well as the diffraction method used for phase determination, which is a helpful tool for the explanation of the important points in the thermo-derivative analysis curve, where the relation between the amount of phase and the occurrence of new phases can be determined.

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