Grains Dendritic

Microstructure after casting of Rodent consists of grains/dendrites sizes up to a few hundred micrometers. Inside the grains are imiformly distributed second phase precipitations that originated during alloy solidification as a result of a superfusion on growing dendrites boimdaries (Fig. la). 

Nuri et al. (1982) reported on the characteristics of rare-earth-added steels, especially the solidification microstructure (including the spacing, length and inclination of dendrite arms) and microsegregation with some consideration of the relevant mechanisms. Microstructural observations revealed that in the rare-earth-added steel fine-grained dendrites at the surface develop extensively, with the adjoining columnar dendrites growing less than those in rare-earth-ffee steel. This difference in the solidification structure has an effect on the secondary structure after solidification. 

Fig. 7. (a) Impurity elements are rejected into the Hquid between the dendritic solidification fronts, (b) Corresponding impurity concentration profiles. Cq, weld metal composition k, impurity partitioning coefficient in the Hquid maximum impurity soHd solubiHty eutectic composition at grain... 

Other authors (2) prefer a different grain structural classification. Specifically, these classifications are (1) columnar, (2) equiaxed, (3) dendritic, (4) nodular, and (5) fibrous. This classification is more in terms of overall structure than in terms of macroscopic and physical properties. 

Dendritic. In electrodeposited films, dendritic grains result from mass-transport-controlled growth, and the individual crystals may vary in shape. 

Dimitrov etal. [370] have investigated initial steps of silver deposition from nitrate solutions on silver and platinum substrates. Growth of independent large Ag grains was observed at lower overpotentials, while at higher overpotentials, dendrites were formed. 

The phase-field simulations reproduce a wide range of microstructural phenomena such as dendrite formation in supercooled fixed-stoichiometry systems [10], dendrite formation and segregation patterns in constitutionally supercooled alloy systems [11], elastic interactions between precipitates [12], and polycrystalline solidification, impingement, and grain growth [6]. 

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