Karel Michalek

Experimental verification of hematite ingot mould heat capacity and its direct utilisation in simulation of casting process

Heat capacity of alloys (metals) is one of the crucial thermophysical parameters used for process behaviour prediction in many applications. Heat capacity is an input variable for many thermodynamical (e.g. Thermocalc, Pandat, MTData, …) and kinetic programs (e.g. IDS-Solidification analysis package, …). The dependences of heat capacity on common variables (temperature, pressure, ...) are also commonly used as the input data in software packages (e.g. ProCast, Magmasoft, ANSYS Fluent, …) that are applicable in the field of applied research for simulations of technological processes. It follows from the above that the heat capacities of materials, alloys in our case, play a very important role in the field of basic and applied research. Generally speaking, experimental data can be found in the literature, but corresponding (needed) data for the given alloy can very seldom be found or can differ from the tabulated ones. The knowledge of proper values of heat capacities of alloys at the corresponding temperature can be substantially used for addition to and thus towards the precision of the existing database and simulation software. This study presents the values of Cp measured for the hematite ingot mould and comparison of the measured data with the Cp values obtained using the software CompuTherm with respect to simulation of technological casting process.

TiAlV/Al2O3/TiNi shape memory alloy smart composite biomaterials for orthopedic surgery

Abstract The structure and properties of TiNi/Al 2 O 3 /Ti-alloy composite implant materials consisting of a Ti-alloy body and active TiNi shape memory elements is discussed The structure of composites and ceramic/metal interfaces were evaluated by scanning electron microscopy (SEM), transmission electron microscopy (TEM), accompanied with energy and wave dispersive X-ray microanalysis (EDX, WDX). Mechanical testing of composite materials was performed using an Inova tensile/compression test machine. Bone/implant interaction and design parameters are also discussed. The structure of the TiNi alloy is modified in the casting process. Similar effects to those observed in the annealing process occurred in TiNi materials during casting and cooling of composites. The Ti-alloy matrix is composed of a mixture of α and β phases. The interaction between the ceramic layer and the metallic components depends on the cooling rate in the casting process. Different reaction products were identified on the Al 2 O 3 /metal interface with dependence on the applied cooling rate of the composite. The fatigue life of the investigated composites is greater than 10 7 cycles, and mechanical properties are sufficient to carry loads expected in human medicine. A newly developed smart implant enables quasielastic fixation with an active role of bone tissue in load carrying process, which has a positive impact on treatment.

Evaluation of Chemical and Structural Heterogeneity in a Continuously Cast Steel Billet

Crystallization of metallic materials occurs during their casting and following solidification. The influence of directional material solidification, the size of grains, chemical heterogeneity and existence of any non – compactness, can negatively affect properties of the final product. Microstructural analysis of its longitudinal section was performed to study heterogeneity in a continuously cast steel billet. Three typical areas of the cast structure of the billet were monitored (the chill zone, columnar crystals area and central area of equiaxed crystals). EDX microanalysis and micro-structural analysis were used for evaluation of chemical heterogeneity. Via X-ray microanalysis, concentrations of the following elements were observed: manganese, chromium, silicon, phosphorus, molybdenum and iron. The microanalytical measurements were completed by microhardness measurements in the investigated areas. Based on the measured data it was proven that central areas were enriched with all the substitutional elements including a considerable increase in phosphorus concentration.

Study of macro-segregations in a continuously cast billet

Ta clanek obravnava studij makro-izcej na vzdolžnem prerezu kontinuirno ulite gredice O 160 mm namenjene za proizvodnjo brezsivnih cevi. Ocena je sestavljena iz vizuelnega pregleda po makrojedkanju, iz ocene in kvantitativne rentgenske mikroanalize s pomocjo energijsko disperzijske rentgenske analize (EDX) izbranih podrocij. Izracunani so bili tudi parametri izcejanja s pomocjo podatkov zgorevne analize. Rezultati, prikazani v tem clanku, predstavljajo osnovno informacijo o notranji strukturi v kontinuirno uliti gredici. Rezultati bodo uporabljeni, poleg drugega, tudi za preverjanje rezultatov numericnega modeliranja kontinuirno ulitih gredic.

Thermal Analysis Results and the Theoretical Determination of Solidus and Liquidus Temperatures for the Grain Oriented Electrical Steel

This paper is devoted to the comparison of theoretically defined solidus and liquidus temperatures based on above mentioned theoretical methods with the results of high-temperature thermal analysis carried out on two devices (Netzsch STA 449 F3 Jupiter; Setaram SETSYS 18TM). On large samples (23 g), the method of direct thermal analysis was applied. On small samples (200 mg), the experiments using differential thermal analysis were realized. It was found out that the solidus and liquidus temperatures for the studied steel grade can vary in dependence on the used determination method. The used methodology of thermal analysis is fully reproducible, and the these thermo-analytical results can be considered as necessary for the correct setting of critical parameters in applied research on the process of steel casting.