Competitive formation of b.c.c.- and {sigma}-phases in undercooled Co-V and Re-W melts
- Commissariat a l`Energie Atomique, Grenoble (France). Centre d`Etudes Nucleaires
- Deutsche Forschunganstalt fuer Luft- und Raumfahrt, Koeln (Germany). Inst. fuer Raumsimulation
Studies on nucleation and competitive phase formation behavior in undercooled bulk melts were performed on the alloy systems Co-V and Re-W. The selected compositions are located within and near the {sigma}-phase domains of both equilibrium phase diagrams. Two different containerless processing techniques were applied: the electromagnetic levitation technique for the undercooling experiments on Co-V, and a long drop-tube for processing the refractory Re-W alloys. Temperature-time profiles during cooling and solidification were recorded by means of rapid photodiode devices in order to extract the dendritic growth velocity of the primarily formed crystalline phases. Steps within the recalescence profiles were observed indicating a favored formation of the metastable b.c.c.-phase instead of the intermetallic compound. Microstructural, Vicker`s hardness and X-ray diffraction studies were performed to obtain a better knowledge of the solidification history. Furthermore, complementary information has been gained by quenching some solidified droplets at different times after recalescence. The results are discussed in the framework of models concerning nucleation and dendritic growth.
- OSTI ID:
- 445334
- Journal Information:
- Acta Materialia, Journal Name: Acta Materialia Journal Issue: 1 Vol. 45; ISSN 1359-6454; ISSN ACMAFD
- Country of Publication:
- United States
- Language:
- English
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