Nucleation and phase selection in undercooled Fe-Cr-Ni melts. Part 2: Containerless solidification experiments
- German Aerospace Research Establishment, Koeln (Germany). Inst. for Space Simulation
- Inst. for Solid State and Materials Research, Dresden (Germany). Inst. for Metallic Materials
The solidification behavior of undercooled Fe-Cr-Ni melts of different compositions is investigated with respect to the competitive formation of {delta}-bcc (ferrite) and {gamma}-fcc phase (austenite). Containerless solidification experiments, electromagnetic levitation melting and drop tube experiments of atomized particles, show that {delta} (bcc) solidification is preferred in the highly undercooled melt even at compositions where {delta} is metastable. Time-resolved detection of the recalescence events during crystallization at different undercooling levels enable the determination of a critical undercooling for the transition to metastable bcc phase solidification in equilibrium fcc-type alloys. Measurements of the growth velocities of stable and metastable phases, as functions of melt undercooling prior to solidification, reveal that phase selection is controlled by nucleation. Phase selection diagrams for solidification processes as function of alloy composition and melt undercooling are derived from two types of experiments: X-ray phase analysis of quenched samples and in situ observations of the recalescence events of undercooled melts. The experimental results fit well with the theoretical predictions of the metastable phase diagram and the improved nucleation theory presented in an earlier article. In particular, the tendency of metastable {delta} phase formation in a wide composition range is confirmed.
- Sponsoring Organization:
- Deutsche Forschungsgemeinschaft, Bonn (Germany); Deutsche Agentur fuer Raumfahrtangelegenheiten (DARA) GmbH, Bonn (Germany)
- OSTI ID:
- 474126
- Journal Information:
- Metallurgical and Materials Transactions. A, Physical Metallurgy and Materials Science, Journal Name: Metallurgical and Materials Transactions. A, Physical Metallurgy and Materials Science Journal Issue: 2 Vol. 28; ISSN MMTAEB; ISSN 1073-5623
- Country of Publication:
- United States
- Language:
- English
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