Nucleation and phase selection in undercooled Fe-Cr-Ni melts: Part II. Containerless solidification experiments |
| |
Authors: | T Volkmann D M Herlach W Löser |
| |
Affiliation: | 1. the Institute for Space Simulation, German Aerospace Research Establishment (DLR), D-51170, K?ln, Germany 2. the Institute for Solid State and Materials Research (IFW), Institute for Metallic Materials, D-01171, Dresden, Germany
|
| |
Abstract: | The solidification behavior of undercooled Fe-Cr-Ni melts of different compositions is investigated with respect to the competitive
formation of δ-bcc (ferrite) and γ-fcc phase (austenite). Containerless solidification experiments, electromagnetic levitation melting and drop tube experiments
of atomized particles, show that δ (bcc) solidification is preferred in the highly undercooled melt even at compositions where δ 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 solidifcation 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 functions 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 δ phase formation in a wide composition range is confirmed. |
| |
Keywords: | |
本文献已被 SpringerLink 等数据库收录! |
|