The mechanism of formation of a fine duplex microstructure in Ti-48Al-2Mn-2Nb alloys
- Oak Ridge National Lab., TN (United States). Metals and Ceramics Div.
The mechanism of formation of the fine duplex microstructure resulting from the {alpha} {yields} {gamma} transformation in water-quenched Ti-48Al-2Mn-2Nb alloys was studied using transmission and analytical electron microscopy. As-cast Ti-48Al-2Mn-2Nb alloys were heat treated in the {alpha} phase field and water quenched to room temperature. The resulting microstructure (referred to as a fine duplex microstructure) consisted of equiaxed grains and abutting lath colonies. Both the colonies and the grains were composed of the {gamma} phase, twinned {gamma} laths, and {alpha}{sub 2} laths. It was found that the transformation from {alpha} to {gamma} in the fine duplex microstructure took place through long range diffusional processes, and competitive growth between the equiaxed and lath morphology occurred. Nucleation of the {gamma} phase from the {alpha} matrix can occur through nucleation on stacking faults, followed by growth through the sympathetic nucleation and growth of new {gamma} laths on a substrate lath. The observed misorientations and the interfacial structures between the laths were found to be consistent with such a mechanism. Competition between such nucleation and growth mechanisms for the equiaxed and lath morphologies of {gamma} leads to the formation of lath colonies (of {gamma} and {alpha}{sub 2}) interspersed with equiaxed grains in these alloys.
- Sponsoring Organization:
- USDOE
- DOE Contract Number:
- AC05-84OR21400
- OSTI ID:
- 264083
- Report Number(s):
- CONF-941016--
- Journal Information:
- Metallurgical Transactions, A, Journal Name: Metallurgical Transactions, A Journal Issue: 6 Vol. 27; ISSN MTTABN; ISSN 0360-2133
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
36 MATERIALS SCIENCE
ALUMINIUM ALLOYS
CASTING
DIFFUSION
GAS TURBINE ENGINES
HEAT TREATMENTS
INTERFACES
INTERMETALLIC COMPOUNDS
MANGANESE ALLOYS
MATERIALS
MICROSTRUCTURE
MORPHOLOGY
NIOBIUM ALLOYS
NUCLEATION
PHASE TRANSFORMATIONS
QUENCHING
SPARK IGNITION ENGINES
STACKING FAULTS
TITANIUM ALLOYS
TRANSMISSION ELECTRON MICROSCOPY