In this paper, the deviation from eutectic composition in boundary layer for eutectic growth is studied by phase-field method. According to a series of artificial phase diagram, the lamellar eutectic growth of these alloy is simulated during directional solidification. At steady state, average growth velocity of eutectic lamella is equal to the pulling velocity. With the increasing of the liquidus slope of β phase, the average composition in boundary layer would deviate from eutectic composition and the deviation increases. The constitutional undercooling difference between both solid phases caused by the deviation increases with the increasing of the deviation. The β phase would develop a depression under the influence of the deviation.

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.

The effect of combination grain refinement with AlTi5B1 master (55 ppm) and Sr-modification with AlSr5 master (20, 30, 40, 50 and 60 ppm) on the microstructure, tensile and hardness properties of AlSi7MgTi cast alloy were systematically investigated. Eutectic silicon was studied by optical and scanning electron microscopy after standard (0.5% HF) and deep etching (HCl). Morphology of eutectic Si changes from compact plate-like (as-cast state) to fibbers (after modification). Si-fibbers in samples with 50 and 60 ppm Sr coarsen probably as a result of over-modification. The optimum mechanical properties has the experimental material which was grain refined and modified with 40 ppm of Sr (UTS = 220.6 MPa; ductility = 6.1%, and 82.3 HBW 5/250/15).

In order to determine the leading phase of the Fe - 4.25% C eutectic alloy, the method of directional crystallization, which allows to study the character of the solid / liquid growth front, was used. Examined eutectic was directionally solidified with a constant temperature gradient of G = 33,5 K/mm and growth rate of v = 125 μm/s (450 mm/h). The Bridgman technique was used for the solidification process. The sample was grown by pulling it downwards up to 30 mm in length. The alloy quenched by rapid pulling down into the Ga-In-Sn liquid metal. The sample was examined on the longitudinal section using a light microscope and scanning electron microscope. The shape of the solid/liquid interface and particularly the leading phase protrusion were revealed. The formation of the concave – convex interface has been identified in the quasi-regular eutectic growth arrested by quenching. The cementite phase was determined to be a leading phase. The total protrusion d is marked in the adequate figure.

In Part I of this article, two-stage solidification model was presented. In this part we use our model to simulate solidification of the Al 7% Si alloy for two cooling rates and . Simulations have been performed for two eutectic transformation modes, typical for modified and unmodified alloys. Obtained cooling curves are qualitatively consistent with the typical cooling curves for modified and unmodified alloys. Moreover, evolution of cooling-curve characteristics is compared with the analytical model and found to be in close agreement.

Studies were conducted on a zinc coating produced on the surface of ductile iron grade EN-GJS-500-7 to determine the eutectic grain

effect. For this purpose, castings with a wall thickness of 5 to 30 mm were made and the resulting structure was examined. To obtain a

homogeneous metal matrix, samples were subjected to a ferritising annealing treatment. To enlarge the reaction surface, the top layer was

removed from casting by machining. Then hot dip galvanising treatment was performed at 450°C to capture the kinetics of growth of the

zinc coating (in the period from 60 to 600 seconds). Analysing the test results it was found that within the same time of hot dip

galvanising, the differences in the resulting zinc coating thickness on samples taken from castings with different wall cross-sections were

small but could, particularly for shorter times of treatment, reduce the continuity of the alloyed layer of the zinc coating.

Some eutectic stripes have been generated in a hexagonal (Zn) - single crystal. The stripes are situated periodically with the constant interstripes

spacing. The eutectic structure in the stripes consists of strengthening inter-metallic compound, Zn16Ti, and (Zn) – solid solution.

The rod-like irregular eutectic structure (with branches) appears at low growth rates. The regular lamellar eutectic structure is observed at

middle growth rates. The regular rod-like eutectic structure exists exclusively in the stripes at some elevated growth rates. A new

thermodynamic criterion is recommended. It suggests that this eutectic regular structure is the winner in a morphological competition for

which the minimum entropy production is lower. A competition between the regular rod-like and the regular lamellar eutectic growth is

described by means of the proposed criterion. The formation of branches within irregular eutectic structure is referred to the state of

marginal stability. A continuous transitions from the marginal stability to the stationary state are confirmed by the continuous

transformations of the irregular eutectic structure into the regular one.

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.

Directional solidification of the Fe - 4,3 wt % C alloy was performed with the pulling rate equal to v=83 μm/s. Sample was frozen during

solidification to reveal the shape of the solid/liquid interface. Structures eutectic pyramid and spherolitic eutectic were observed. The

solidification front of ledeburite eutectic was revealed. The leading phase was identified and defined.

This article focuses on the study of the influence of remelting and subsequent natural and artificial ageing on the structure of recycled AlSi9Cu3 alloy with increased iron content. The assessed changes in eutectic silicon and iron-based intermetallic phases were carried out using optical and scanning electron microscopy. The degradation of the eutectic silicon morphology due to remelting occurred only at the highest numbers of remelting. The effect of remelting the investigated alloy, which is accompanied by a gradual increase in wt. % Fe, began to manifest significantly through a change in the length of the ferric phases after the fourth remelting. As expected, the artificial ageing process has proven to be more effective than natural ageing. It has led to a change in the eutectic silicon morphology and has been beneficial in reducing the lengths of adverse ferric phases. The use of alloys with higher numbers of remelting, or with greater “contamination”, for the manufacture of shape-challenging castings is possible when using a suitable method of eliminating the negative factors of the remelting process. The results of our investigation show a suitable method of the above elimination the application of heat treatment T5 – via artificial ageing.

The paper presents adaptation problem of lamellar/rod growth of eutectic. The transformation of eutectic microstructure was investigated systematically. A interpretation of the eutectic growth with theory minimum entropy production was presented.

The paper presents a new numerical model of solidification processes in hypoeutectic alloys. The model combines stochastic elements, such as e.g. random nucleation sites and orientation of dendritic grains, as well as deterministic methods e.g. to compute velocity of dendritic tips and eutectic grains. The model can be used to determine the temperature and the size of structure constituents (of both, the primary solid phase and eutectics) and the arrangement of individual dendritic and eutectic grains in the consecutive stages of solidification. Two eutectic transformation modes, typical to modified and unmodified hypoeutectic alloys, have been included in the model. To achieve this, cellular automata and Voronoi diagrams have been utilized.

In a vacuum Bridgman-type furnace, under an argon atmosphere, directionally solidified sample of Fe - C alloy was produced. The pulling

rate was v = 83 μm/s (300 mm/h) and constant temperature gradient G = 33,5 K/mm. The microstructure of the sample was examined on

the longitudinal section using an Optical Microscope and Scanning Electron Microscope. The X-ray diffraction and electron backscatter

diffraction technique (EBSD) have been used for the crystallographic analysis of carbide particles in carbide eutectic. The

X-ray diffraction was made parallel and perpendicular to the axis of the goniometer. The EBSD shows the existence of iron carbide Fe3C

with orthorhombic and hexagonal structure. Rapid solidification may cause a deformation of the lattice plane which is indicated by

different values of the lattice parameters. Such deformation could also be the result of directional solidification. Not all of the peaks in

X–ray diffractograms were identified. They may come from other iron carbides. These unrecognized peaks may also be a result of the

residual impurity of alloy.

The entropy production per unit time is calculated for the regular lamellae -, and for the regular rods formation, respectively. The entropy production is a function of some parameters which define the eutectic phase diagram, coefficient of the diffusion in the liquid, and some capillary parameters connected with the mechanical equilibrium located at the triple point of the solid/liquid interface. Minimization of the entropy production allowed to formulate mathematically the so-called Growth Law for both envisaged eutectic morphologies.

In this study, the effects of grain size refiner addition and various pre-heating mold temperatures on AlSi9 cast alloy microstructure and solidification have been evaluated. For different process conditions, thermal analysis was performed for all samples and cooling curves were established. Important parameters in liquidus and eutectic Si-phase regions have been calculated using the first derivative cooling curves. Secondary Dendrite Arm Spacing (SDAS) variation was also determined. Experimental results question the effectiveness of cooling curve parameters in providing the microstructure data as a function of refinement. The present work shows that the effect of grain refiner addition on the value of SDAS was higher when the solidification time was lower. It indicated that the solidification parameters such as nucleation temperatures of α-Al phase, undercooling temperature and total solidification time were affected by grain refinement. It has been found that the addition of grain refiner affect the eutectic phase formation time. However, it has no effect on the eutectic phase morphology.