Superplastic behavior in a powder-metallurgy TiAl alloy with a metastable microstructure
Superplasticity in a powder-metallurgy TiAl alloy (Ti-47Al-2Cr-2Nb) with a metastable microstructure has been studied. Samples were tested at temperatures ranging from 650 to 1100{degrees}C, and at strain rate ranging from 10{sup -6} to 10{sup -4} s{sup -1}. An elongation value of over 300 obtained at a strain rate of 2 x 10{sup -5} s{sup -1} and at a temperature as lo as 800{degrees}C, which is close to the ductile-to-brittle-transition temperature. This is in contrast to the prior major observations of superplastic behaviors in TiAl in which typical temperatures of 1000{degrees}C have usually been required for superplasticity. It is proposed that the occurrence of superplasticity at 8000{degrees}C in the present alloy is caused by the presence of a B2 phase. During superplastic deformation (grain boundary sliding), the soft P grains accommodate sliding strains to reduce the propensity for cavitation at grain triple junctions and, thus, delays the fracture process. The final microstructure consists of stable, equiaxed y+a{sub 2} grains.
- Research Organization:
- Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)
- Sponsoring Organization:
- USDOE Office of Energy Research, Washington, DC (United States); Department of the Army, Washington, DC (United States)
- DOE Contract Number:
- W-7405-ENG-48
- OSTI ID:
- 328524
- Report Number(s):
- UCRL-JC-129442; CONF-9804102-; ON: DE98054503; BR: KC0201050
- Resource Relation:
- Conference: 3. international workshop on ordered intermetallic alloys and composites, Hongzhon (China), 5-10 Apr 1998; Other Information: PBD: Dec 1997
- Country of Publication:
- United States
- Language:
- English
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