An Analysis of the Role of Grain Size on Superplasticity of Γ Titanium Aluminides
The superplastic data for several microcrystalline and submicrocrystalline TiAl alloys has been analyzed to establish the rate controlling mechanism. The results show that the lattice diffusion controlled slip-accommodated grain boundary sliding mechanism is operative for the entire grain size range, 150 nm-20 micro-m. The detail of the nature of alpha2 phase, i.e. Ordered or disordered, does not influence the kinetics of superplastic flow. The optimum superplastic temperature decreases with the decrease in grain size. The optimum superplastic flow stress shows an intrinsic inverse dependence on the grain size. This grain size dependence of the optimum superplastic flow stress can be explained as the stress required to nucleate dislocations from grain boundary edge during slip accommodation of grain boundary sliding. Superplasticity in nanocrystalline TiAl remains an intriguing possibility because it has the potential for increasing the optimal superplastic strain rate or alternatively, decreasing the superplastic forming temperatures.
R. S. Mishra and A. K. Mukherjee, "An Analysis of the Role of Grain Size on Superplasticity of Γ Titanium Aluminides," Journal of Materials Science, Springer Verlag, Jan 2000.
The definitive version is available at http://dx.doi.org/10.1023/A:1004713220757
Materials Science and Engineering
National Science Foundation (U.S.)
Keywords and Phrases
Titanium Aluminides; Alloys; Superplasticity
Article - Journal
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