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Influence of strain rate and temperature on the deformation mechanisms of a fine-grained Ti-6Al-4V alloy

Despax, Laurie and Vidal, Vanessa and Delagnes, Denis and Dehmas, Moukrane and Matsumoto, Hiroaki and Velay, Vincent Lionel Sébastien Influence of strain rate and temperature on the deformation mechanisms of a fine-grained Ti-6Al-4V alloy. (2020) Materials Science and Engineering A, 790. 139718. ISSN 0921-5093

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Official URL: https://doi.org/10.1016/J.MSEA.2020.139718

Abstract

Depending on their initial microstructure, titanium alloys, as the Ti-6Al-4V may have activation of different deformation mechanisms during hot forming processes. In this work, interrupted tensile tests and heat treatments are used to improve the understanding of the mechanical and microstructural behaviour of a fine-grained Ti-6Al-4V alloy at two temperatures (750 and 920 ) and so for two different phase fractions. The microstructural features like, grain size and phase fraction, were determined by Scanning Electron Microscope (SEM) and image analysis. Moreover, evolution of the preferred crystallographic orientation of grains and local misorientations between and inside grains were obtained by Electron Backscatter Diffraction (EBSD). The strain rate sensitivity parameter as well as the activation energy were deduced from mechanical tests. It appears, from all these microstructural and mechanical data, that several mechanisms are activated depending on the strain level and on the temperature range. At 750 , for a high strain rate, the deformation is mainly controlled by dislocations activity in the phase (texture changes, dynamic recrystallization) and, at very low strain rate, by probably GBS accommodated with dislocations activity into (recovery) and . On the contrary at 920 , a clear decrease of the overall texture intensity associated with a high value suggests that GBS is the dominant mode of deformation. Nevertheless, as the volume fraction is around 48 %/52 % at this temperature, not only the phase but also the phase as well as and boundaries might contribute to the flow behaviour. During long deformation time (low strain rate and high temperature), dynamic coarsening behaviour (both into and ), that is controlled by bulk diffusion, can occur and modify the type, the distribution and decrease the number of , and boundaries. This can be partly related to the flow hardening observed at 920 and 10−4 s−1.

Item Type:Article
HAL Id:hal-03033092
Audience (journal):International peer-reviewed journal
Uncontrolled Keywords:
Institution:Other partners > Kagawa University (JAPAN)
French research institutions > Centre National de la Recherche Scientifique - CNRS (FRANCE)
Université de Toulouse > Ecole nationale supérieure des Mines d'Albi-Carmaux - IMT Mines Albi (FRANCE)
Université de Toulouse > Institut National Polytechnique de Toulouse - Toulouse INP (FRANCE)
Université de Toulouse > Institut National des Sciences Appliquées de Toulouse - INSA (FRANCE)
Université de Toulouse > Institut Supérieur de l'Aéronautique et de l'Espace - ISAE-SUPAERO (FRANCE)
Université de Toulouse > Université Toulouse III - Paul Sabatier - UT3 (FRANCE)
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Deposited On:15 Oct 2020 12:36

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