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EN
Directionally solidified sample of Fe-Fe3C eutectic alloy were produced under an argon atmosphere in a vacuum Bridgman-type furnace to study the eutectic growth with v = 167 μm/s pulling rate and constant temperature gradient G = 33.5 K/mm. Since how the growth texture of eutectic cementite is related to its growth morphology remains unclear, the current study aims to examine this relationship. The technique such as X-ray diffraction, have been used for the crystallographic analysis of carbide particles in white cast irons.
EN
The, developed in this study, simple model and numerical solution of diffusion growth of the solid phase under the conditions of directional solidification allow for the effect of constituent diffusion in both liquid and solid phase and assume the process run in which (like in reality) the preset parameter is the velocity of sample (pulling velocity) at a preset temperature gradient. The solid/liquid interface velocity is not the process parameter (like it is in numerous other solutions proposed so far) but a function of this process. The effect of convection outside the diffusion layer has been included in mass balance under the assumption that in the zone of convection the mixing is complete. The above assumptions enabled solving the kinetics of growth of the solid phase (along with the diffusion field in solid and liquid phase) under the conditions of diffusion well reflecting the process run starting with the initial transient state, going through the steady state period in central part of the casting, and ending in a terminal transient state. In the numerical solution obtained by the finite difference method with variable grid dimensions, the error of the mass control balance over the whole process range was 1- 2%.
PL
Dla aluminium i jego stopów z krzemem przedstawiono skaningowe obrazy frontu krystalizacji strugi krzepnącej w kanale formy metalowej.
EN
For aluminum and aluminum-silicon alloys flowing and solidifying in metal mould channel the SEM-micrographs of crystallization interface have been presented.
EN
A eutectic reaction is a basic liquid-solid transformation, which can be used in the fabrication of high-strength in situ composites. In this study an attempt was made to ensure directional solidification of Fe-C-V alloy with hypereutectic microstructure. In this alloy, the crystallisation of regular fibrous eutectic and primary carbides with the shape of non-faceted dendrites takes place. According to the data given in technical literature, this type of eutectic is suitable for the fabrication of in-situ composites, owing to the fact that a flat solidification front is formed accompanied by the presence of two phases, where one of the phases can crystallise in the form of elongated fibres. In the present study an attempt was also made to produce directionally solidifying vanadium eutectic using an apparatus with a very high temperature gradient amounting to 380 W/cm at a rate of 3 mm/h. Alloy microstructure was examined in both the initial state and after directional solidification. It was demonstrated that the resulting microstructure is of a non-homogeneous character, and the process of directional solidification leads to an oriented arrangement of both the eutectic fibres and primary carbides.
EN
Purpose: The specifics of the influence of alloying elements on the chemical composition of various types of carbides, their topology and morphology for a multicomponent system of the type Ni-5Cr-9Co-6Al-1Ti-11.7W-1.1Mo-1.6Nb-0.15C using the calculation method CALPHAD. It is shown that the obtained dependences closely correlate with thermodynamic processes occurring in the system. Design/methodology/approach: This work presents the results of studies of the distribution of chemical elements in the composition of carbides, depending on their content in the system. Findings: It was found that the influence of alloying elements on the composition of carbides is complex and is described by complex. Research limitations/implications: An essential problem is the prediction of the structure and properties of heat-resistant alloys without or with a minimum number of experiments. Practical implications: The obtained dependences can be used both for designing new heat-resistant alloys and for improving the compositions of industrial alloys. Originality/value: The value of this work is that the obtained dependences of the influence of alloying elements on the dissolution (precipitation) temperatures and the distribution of elements in carbides in the alloy of the Ni-5Cr-9Co-6Al-1Ti-11.7W-1.1Mo-1.6Nb-0.15C.
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