Abstract
Heterogeneous nuclei may be present in high concentration in the undercooled melt and could certainly require a higher cooling rate Ṫ than in the case of pure homogeneous nucleation process to avoid crystallization. The critical cooling rate T ̇ c required for glassy solidification of a Pd 77.5Cu 6Si 16.5 alloy was measured by monitoring the critical velocity v c for the formation of amorphous structure during the directional solidification. The measured T ̇ c = 221 K s −1 was higher than the Ṫ c value computed from a continuous-cooling-transformation (CCT) diagram using the Uhlmann treatment considering only homogeneous nucleation. The nucleation and growth during devitrification of a glassy sample were studied in comparison with another glassy sample produced in a drop tube. The existence of about 4 × 10 11 heterogeneous nuclei m −3 was estimated and could explain the high experimental T ̇ c value. Microstructures show typical heterogeneous nucleation observed in the samples, illustrating the effect of container walls and motes on the solidification process.
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Disclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.