High strain torsion of a TiAl-based alloy

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• 作者：G.H. Cao ; B. Klö ; den ; E. Rybacki ; C.-G. Oertel ; W. Skrotzki
• 关键词：TiAl ; Torsion ; Microstructure ; Texture ; Superplasticity
• 刊名：Materials Science and Engineering: A
• 出版年：2008
• 出版时间：15 June 2008
• 年：2008
• 卷：483-484
• 期：Complete
• 页码：512-516
• 全文大小：738 K

文摘

A two-phase lamellar and globular TiAl-based alloy (Ti–45Al–4(Cr, Nb, Ta, B)) with different textures has been deformed in torsion in a Paterson-type rock deformation machine at a temperature of 1173 K under 400 MPa argon confining pressure. The shear stress–shear strain curves with increasing shear strain show a decrease or increase of shear stress in the lamellar and globular case, respectively, to a common steady state value. Activation analysis at high strains yields stress exponents of about 1.8 and an activation energy of 3.29 eV. With increasing shear strain the lamellar structure breaks down and a two-phase fine-grained globular structure develops by recrystallization with a grain size in the order of 2 μm. The weak initial fibre textures at high strains are randomized. The mechanical, microstructural and textural features indicate a transition from dislocation creep to superplastic flow.