Modeling of micro- and macrosegregation and freckle formation in single-crystal nickel-base superalloy directional solidification
- Univ. of Iowa, Iowa City, IA (United States). Dept. of Mechanical Engineering
- NIST, Gaithersburg, MD (United States). Metallurgy Div.
The formation of macrosegregation and freckles by multicomponent thermosolutal convection during the directional solidification of single-crystal Ni-base superalloys is numerically simulated. The model links a previously developed thermodynamic phase equilibrium subroutine with an existing code for simultaneously solving the macroscopic mass, momentum, energy, and species conservation equations for solidification of a multicomponent alloy. Simulation results are presented for a variety of casting speeds and imposed thermal gradients and for two alloy compositions. It is found that for a given alloy composition, the onset of convection and freckle formation occurs at a critical primary dendrite arm spacing, which agrees well with previous experimental findings. The predicted number and shape of the freckle chains in the unstable cases also agree qualitatively with experimental observations. Finally, it is demonstrated how the onset and nature of convection and macrosegregation vary with alloy composition. It is concluded that the present model can provide a valuable tool in predicting freckle defects in directional solidification of Ni-base superalloys.
- Sponsoring Organization:
- Advanced Research Projects Agency, Washington, DC (United States); National Science Foundation, Washington, DC (United States)
- OSTI ID:
- 522363
- 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: 7 Vol. 28; ISSN 1073-5623; ISSN MMTAEB
- Country of Publication:
- United States
- Language:
- English
Similar Records
Modeling freckle formation in three dimensions during solidification of multicomponent alloys
The breakdown of single-crystal solidification in high refractory nickel-base alloys