Dendritic and eutectic solidification of undercooled Co-Sb alloys
- Inst. fuer Raumsimulation, Stuggart (Germany)
- Max-Planck-Inst. fuer Metallforschung, Stuttgart (Germany)
Co-20- wt% Sb hypoeutectic, Co-41.4 st% Sb eutectic, and Co-45 wt% Sb hypereutectic alloys were undercooled by up to 224, 225 and 177 K, respectively. The dendritic and eutectic growth velocities during rapid solidification were measured by an infrared technique. It is found that dendrite growth in the hypoeutectic alloy is still in the regime of solute diffusion-controlled growth even at an undercooling of 224 K. A dendritic-equiaxed'' microstructure transition occurs if this hypoeutectic alloy is undercooled by more than 90 K, resulting in an abrupt grain refinement effect. Two undercooling thresholds were observed for the eutectic alloy: below the lower limit of [Delta]T[sup [asterisk]][sub e1] = 50 K lamellar eutectic is the unique growth morphology; above the upper limit of [Delta]T[sup [asterisk]][sub e2] = 150K only anomalous eutectic can grow. Although anomalous eutectic is the product of rapid solidification, it shows much greater thermodynamic stability than the lamellar eutectic formed under slow solidification conditions. The hypereutectic alloy behaves like a eutectic alloy during the rapid solidification at sufficiently large undercoolings.
- OSTI ID:
- 6273620
- Journal Information:
- Acta Metallurgica et Materialia; (United States), Vol. 41:6; ISSN 0956-7151
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
ANTIMONY ALLOYS
SOLIDIFICATION
COBALT BASE ALLOYS
COOLING
CRYSTAL GROWTH
DENDRITES
EUTECTICS
GRAIN REFINEMENT
MICROSTRUCTURE
TEMPERATURE RANGE 0065-0273 K
ALLOYS
COBALT ALLOYS
CRYSTALS
PHASE TRANSFORMATIONS
TEMPERATURE RANGE
360102* - Metals & Alloys- Structure & Phase Studies