A REVIEW STUDY OF NUCLEATION AND ITS ROLE IN SOLIDIFICATION.
Abstract
A review study of nucleation and its role in determining grain size in solidification is presented. It is demonstrated that nucleation is an essential aspect of most phase transformation processes when the unstable phase is initially free of all fragments of the more stable phase to be formed. Occurrence of multi-nucleation events for many transformations; the required maintenance of a critical metastability for continued classical nucleation; and the feedback effect of crystal or cluster growth tending to destroy this metastability are emphasized. Limitation of grain density to the density of growth centers which can be generated by nucleation and then maintained is discussed. Secondary nucleation, which includes such processes as crystal fragmentation, is emphasized as a separate route from classical nucleation by which growth centers can be generated. A theoretical analysis of the interaction of homogeneous nucleation and crystal growth under ideal conditions is presented. Preliminary results predict grain density should vary with the 1.45 power of cooling rate. (Author)
Document Details
- Document Type
- Technical Report
- Publication Date
- Jun 15, 1969
- Accession Number
- AD0711932
Entities
People
- Kenneth A. Van Wormer Jr
Organizations
- Tufts University