Superplastic behaviour of Ti-48at.%Al two-phase titanium aluminide compacts made from mechanically alloyed powder |
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Authors: | Kei Ameyama Hitoshi Uno Masaharu Tokizane |
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Affiliation: | Faculty of Science & Engineering, Ritsumeikan University, Kusatso, Shiga 525-77, Japan |
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Abstract: | An HIP compact of MA-processed powder having a nominal composition of Ti-48at.% Al was produced. The compact consisted of a large amount of TiAl(λ) and a small amount of Ti3Al (2), in a completely ultra-fine equiaxed grain structure. This two-phase compact showed typical superplastic deformation behaviour. A maximum elongation of 550% was obtained. A strain exponent, n = 2, and grain size exponent, p = 2, were determined from the results of a strain-rate-change test and a creep test at constant initial stress using samples having various grain sizes, respectively. The activation energy for creep, Qc at constant stress was calculated to be 350 kJ/mole. It is concluded that the superplastic deformation mechanism of the material under study is grain boundary sliding controlled by lattice diffusion in the TiAl phase. |
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Keywords: | superplasticity two-phase titanium aluminide mechanical alloying grain boundary sliding microduplex structure |
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