Materials Science: Unit I: Crystallography
Nucleation and Growth
Crystallography
Nucleation is the beginning of phase transformation.
NUCLEATION AND GROWTH Nucleation is the beginning of phase transformation. It starts tiny regions called nuclei of new phase in the molten metal. The nuclei grows to form the solid crystal until the transformations is complete. Nucleation may involve: 1. The assembly of atoms by diffusion. 2. Structural change into one or more unstable intermediate structures. 3. Formation of critical size particle called nuclei of the new phase (i.e., solid) The process of crystallation mainly consists of following stages. (Fig. 1.54). (a) Formation of Nuclei, (b) Growth of nuclei into crystals; and (c) Joining of crystals to form grains with grain boundaries. There are two main mechanisms by which nucleation of solid particles in liquid metal occurs. 1. Homogeneous Nucleation / Self Nucleation 2. Heterogeneous Nucleation
Materials Science: Unit I: Crystallography : Tag: : Crystallography - Nucleation and Growth
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