Columnar microstructure, development

In Chapter 7 various growth models were described layer growth (Section 7.9), nucleation-coalescence growth (Section 7.10), development of texture (Section 7.11), columnar microstructure (Section 7.12), and other structural forms (Section 7.13). In this section we discuss the effects of additives on these growth mechanisms. 

As follows from electron diffraction, films of crystalline materials formed on amorphous substrates under normal conditions are generally polycrystalline in their structure. During further thickness growth, a columnar microstructure can often be observed and thicker film may develop a texture. 

Columnar texture is a general rule for film growth. Films develop this microstructure... 

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. 

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