Heterogeneous nucleation and grain formation on substrates of different potency and geometries during solidification

Qian, M. (2007). Heterogeneous nucleation and grain formation on substrates of different potency and geometries during solidification. In: Euromat 2007: European Conference and Exhibition on Advanced Materials and Processes, Nürnberg, Germany, (). 10-13 September 2007.


Author Qian, M.
Title of paper Heterogeneous nucleation and grain formation on substrates of different potency and geometries during solidification
Conference name Euromat 2007: European Conference and Exhibition on Advanced Materials and Processes
Conference location Nürnberg, Germany
Conference dates 10-13 September 2007
Convener Federation of European Materials Societies (FEMS)
Publication Year 2007
Sub-type Fully published paper
Language eng
Formatted Abstract/Summary
The ability to control heterogeneous nucleation lies at the heart of the development of a novel technology or microstructure. The first step towards achieving such an ambition is to understand, as much as possible, how heterogeneous nucleation occurs. A critical review has been made of the various models proposed or employed for understanding crystallisation on substrates of different potency and geometries during solidification since Volmer (1929). These in general can be classified as follows: (i) those for nucleation on less potent substrates by large clusters where a spherical-cap nucleus is assumed; (ii) those for nucleation on potent substrates by adsorption where a thin layer nucleus is anticipated; (iii) those for nucleation on potent substrates by wetting where the shape of the nucleus varies according to the geometry of the substrate. Particular attention has been given to the formation of “transformation nuclei” on less potent flat substrates according to Turnbull’s patch nucleation theory, and the nucleation on potent flat and spherical substrates where the spherical cap assumption appears to break down. Experimental observations are presented of the grain refinement, controlled columnar to equiaxed transition, and creation of spherical primary crystals in magnesium alloys by inoculation with nearly spherical potent zirconium substrates. The observations agree well with a recent model proposed by Qian (Acta Mater 2007;55:943) for nucleation on potent spherical substrates by an adsorption and surface diffusion mechanism.
Subjects 09 Engineering
Q-Index Code EX
Additional Notes Presented as Invited Highlight Lecture C11-1566 and Session Chair. Prepress title: "Heterogeneous nucleation and grain formation on substrates of different potency and geometries".

 
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Created: Fri, 27 Nov 2009, 13:31:10 EST by Ms Lynette Adams on behalf of School of Engineering