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Some factors affecting the atom migration kinetics and nucleation conditions at the solidification interface can lead to the changes of eutectic growth mode and eutectic morphology(brown aluminium oxide suppliers luxembourg). These factors widely exist in the solidification process of cast iron, which is the main reason for the diversity of eutectic structure of cast iron. One phase has precipitated a lot before the other phases begin to grow. 

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Generally, according to the characteristics of eutectic formation process and the morphology of eutectic structure, eutectic structure can be divided into three categories: normal eutectic, abnormal eutectic and divorced eutectic(80 grit aluminum oxide). If the phases are co grown, the undercooling required is basically the same(brown aluminium oxide suppliers luxembourg). Therefore, the concept of synergistic growth cannot be used to explain the process of divorced eutectic transformation. 

It can be seen from the figure that when the liquid phase with equilibrium eutectic composition is subcooled below the equilibrium eutectic temperature(garnet sand), the first precipitation is not eutectic structure, but phase a with low melting point nucleated outside the symbiotic zone, which leads to the increase of component B concentration in the liquid phase and reaches the degree of supersaturation(brown aluminium oxide suppliers luxembourg). 

The growth of this component changes the composition of the melt so that it cannot enter the asymmetric eutectic region(white aluminum oxide). For example, the microstructure of layered cementite formed by iron carbon alloy at a certain growth rate basically conforms to the A-R relationship(180 grit aluminum oxide). As the leading phase, spheroidal graphite of nodular cast iron first precipitates from the liquid phase, then is surrounded by austenite, and continues to grow in the pod shell(brown aluminium oxide suppliers luxembourg). 

The basic condition of normal eutectic is that the co grown constituent phases have rough solidification interface(brown aluminium oxide suppliers luxembourg). There is a suitable crystal orientation relationship between phases, in which the growth of a certain phase can promote the nucleation and growth of synergistic growth phase(steel grid); If the eutectic structure is layered, the growth direction of the lamella is basically perpendicular to the solidification interface.

Abnormal eutectic is not layered structure(brown aluminium oxide suppliers luxembourg). There are flake, rod or other irregular precipitates in the eutectic structure. The eutectic formed by flake graphite and austenite in normal gray cast iron belongs to abnormal eutectic(aluminum oxide for sale). The most remarkable feature of divorced eutectic is that the crystals of each constituent phase of eutectic are separated in space and time, and the crystals grow completely outside the symbiotic zone.

The divorced eutectic transformation occurs in the following situations: the composition of eutectic constituent phases is very different, and the nucleation conditions and crystal growth mode are different(glass bead blasting media suppliers). It can be seen that the layer spacing a (EM) is controlled by the interface growth rate R (EM / s). The layer spacing and growth rate of many normal eutectic accord with a = Kr relationship(brown aluminium oxide suppliers luxembourg). 

However, practice shows that the greater the composition deviation, the more likely it is to produce divorced growth, and the greater the undercooling of Eutectic Transformation(black aluminum oxide). In the process of austenite dendrite growth, changing the cooling rate will lead to the change of dendrite volume fraction and morphology(brown aluminium oxide suppliers luxembourg). The leading phase may be surrounded by a subsequently generated second phase to form a pod shell. 

Specifically, among the multiple phases forming eutectic, the first precipitated crystal can not become the nucleation matrix of the later precipitated phase, or can not start or induce the phase crystallization with difficult nucleation(aluminum oxide sand). When the leading phase grows to a certain extent, the diffusion rate of solute in the liquid phase is very low, so that the concentration between the phases can not reach equilibrium(brown aluminium oxide suppliers luxembourg). 

However, during the solidification of the shell, the leading phase can also grow in a special state through the second phase(aluminium oxide blast media). The Eutectic Transformation of nodular cast iron belongs to the category of divorced eutectic transformation. The difficulty of nucleation may cause the growth of divorced eutectic(brown aluminium oxide suppliers luxembourg). This process can basically reflect the formation process of eutectic structure of flake graphite and spheroidal graphite cast iron. 

Before discussing the eutectic solidification process of cast iron, it is very necessary to understand the eutectic solidification process of iron carbon alloy under non-equilibrium conditions(pink corundum). The carbon concentration of graphite and austenite in ferromagnetic alloy is very different, and the nucleation properties and growth conditions are different(brown aluminium oxide suppliers luxembourg). The symbiotic zone of graphite austenite is an asymmetric symbiotic zone.

The symbiotic zone tends to the hypereutectic side, and its boundary is related to some factors such as metallurgical process and crystallization kinetics(aluminium oxide blasting). The eutectic transformation begins when the carbon concentration in the melt reaches the symbiotic zone of Hypereutectic components(brown aluminium oxide suppliers luxembourg). With the decrease of temperature and the growth of primary dendrite with low carbon content, the composition of molten liquid reaches 2.

Generally, the solidification process of gray cast iron can be explained schematically according to the symbiotic zone model of iron carbon binary alloy(green silicon carbide). When the eutectic Fe-C alloy is undercooled to a certain temperature of equilibrium composition (point in the figure), austenite first nucleates and grows into dendrite(brown aluminium oxide suppliers luxembourg). Therefore, in order to obtain D-type graphite structure, some titanium needs to be added to cast iron.

Therefore, the carbon concentration of molten iron moves to the symbiotic zone with the increase of austenite dendrite (point-to-point in the figure)(alumina sand). At the same time, graphite and austenite grow together to form eutectic clusters(brown aluminium oxide suppliers luxembourg). The eutectic Fe-C alloy solidified under non-equilibrium conditions does not have a single eutectic structure, but is composed of primary austenite and graphite austenite eutectic clusters(70 grit aluminum oxide).

The precipitation amount, size and morphology of primary austenite have a significant effect on the formation of eutectic clusters and the morphology, size and distribution of eutectic graphite, so it is also an important factor to determine the properties of the alloy. The point nucleation of austenite dendrites above eutectic temperature in Hypoeutectic alloys(alumina abrasive). Therefore, the solidification interface is basically isothermal(brown aluminium oxide suppliers luxembourg). 

The growth of graphite is restricted by the self diffusion of iron and silicon atoms(aluminum oxide abrasive powder). Due to high undercooling, graphite begins to nucleate, and eutectic growth takes place in the symbiotic zone(brown aluminium oxide suppliers luxembourg). The phases in the normal common product are regularly overlapped and arranged, which is generally layered structure(black silicon carbide). Due to the different growth mechanism of each phase, the undercooling corresponding to the growth rate is not exactly the same.