Abstract
In order to verify the correctness of the transition of deformation mechanism with the change in deformation parameters and to reveal the types and mechanism of dynamic recrystallization of γ grains during compression deformation, microstructure characterization of Ti-43.5Al-8Nb-0.2W-0.2B (at. %) alloy after isothermal compression deformation were performed. When the alloy was deformed at 1000 °C/10−2 s−1, the initial γ grains are elongated and significantly refined and the fraction of low angle grain boundaries (LAGB) of γ grains is obviously increased and the texture intensity remains unchanged, which indicates that the compression deformation in dislocation creep region is dominated by intragranular deformation and dynamic recrystallization (DRX) of γ grains. Besides, the lattice rotation at grain boundary serrations may be responsible for the nucleation of new recrystallized γ grains, and the following growth process may be achieved by the migration of γ grain boundaries. However, when the alloy deformed at 1050 °C/10−4 s−1 and 1000 °C/10−4 s−1, the γ grains maintain equiaxed shapes and distribute more uniformly and the fraction of LAGB of γ grains is slightly raised and the texture sharpness decreases, which indicates that the compression deformation in grain boundary sliding (GBS) region is mainly controlled by GBS of γ grains and DRX occurs simultaneously within some coarse γ grains.
Highlights
Weight-reduction is becoming more and more critical for structural applications in the aerospace and automotive industries
The variation of texture intensity on deformation parameters indicates that the compression deformation at 1000 ◦ C with the strain rate of 10−2 s−1 in dislocation creep region is dominated by intragranular deformation and DRX of γ grains and the texture intensity remains around 2 via the above Section described DRX model
The main conclusions are summarized below: (1) The elongated initial γ grains and the significantly decreased size of recrystallized γ grains and the obviously increased fraction of low angle grain boundaries (LAGB) of γ grains of the alloy after compression deformation at 1000 ◦ C with the strain rate of 10−2 s−1 indicates that the compression deformation in dislocation creep region is dominated by intragranular dislocations sliding and climbing in γ grains which leading to the occurrence of DRX of γ grains
Summary
Weight-reduction is becoming more and more critical for structural applications in the aerospace and automotive industries. Γ-TiAl based alloys have been widely considered as novel lightweight high-temperature structural materials, which possess high specific strength and stiffness, good resistance against oxidation and corrosion, and good creep properties [3,4]. This kind of intermetallic alloy characterized by mixed metallic and covalent bonding is substantially hard to deform due to its intrinsic brittleness and high flow stress [5,6]. In order to reduce weight, most of the structural components used in aerospace are designed with the complex shape of thin-web and high-rib [1], which are difficult to form, especially for those made of brittle γ-TiAl based alloys. The pioneering research works regarding isothermal compression deformation of γ-TiAl alloys [13,14,15,16,17]
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