Kinetic competition in undercooled liquid alloys
- Univ. of Wisconsin, Madison, WI (United States). Dept. of Materials Science and Engineering
Most alloy systems can develop more than one solid phase for a given composition during solidification. For metastable undercooled liquids a thermodynamic analysis can provide insight into the range of structural and compositional options that are possible. The numerous examples of metastable phase formation during solidification of undercooled melts demonstrates that the actual phase selection is dominated by kinetics. Indeed, the observation of undercooling is linked to kinetic control. Different forms of kinetic control can be identified and include suppression of heterogeneous nucleation during slow cooling and constrained growth during rapid quenching. In both cases the kinetic competition involved in phase selection is mediated by the thermal history. Nucleation controlled kinetics can be examined in fine powders of undercooled liquids where crystallization rates and metastable phase diagrams provide a basis for analysis. Similarly, constrained growth can be examined during controlled cooling where microstructures and kinetic models can be used for analysis. The existing kinetics models appear to be adequate but the processing conditions are often dynamic and in nonsteady state conditions so that critical tests are difficult unless specific kinetic transitions are available.
- Sponsoring Organization:
- Department of the Army, Washington, DC (United States); National Aeronautics and Space Administration, Washington, DC (United States)
- OSTI ID:
- 479241
- Report Number(s):
- CONF-951155-; ISBN 1-55899-301-0; TRN: IM9725%%2
- Resource Relation:
- Conference: Fall meeting of the Materials Research Society (MRS), Boston, MA (United States), 27 Nov - 1 Dec 1995; Other Information: PBD: 1996; Related Information: Is Part Of Thermodynamics and kinetics of phase transformations; Im, J.S. [ed.] [Columbia Univ., New York, NY (United States)]; Park, B. [ed.] [Georgia Inst. of Tech., Atlanta, GA (United States)]; Greer, A.L. [ed.] [Cambridge Univ. (United Kingdom)]; Stephenson, G.B. [ed.] [Argonne National Lab., IL (United States)]; PB: 697 p.; Materials Research Society symposium proceedings, Volume 398
- Country of Publication:
- United States
- Language:
- English
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