MATEC Web Conf.
Volume 321, 2020The 14th World Conference on Titanium (Ti 2019)
|Number of page(s)||7|
|Published online||12 October 2020|
MICROSTRUCTURAL EVOLUTIONS AND MECHANICAL PROPERTIES DURING LONG-TERM AGEING OF TITANIUM ALLOY Ti-17
1 AIRBUS, Toulouse, France
2 Université de Lorraine, CNRS, IJL, Nancy, France
3 APSYS-AIRBUS, Vitrolles, France
4 CIRIMAT, Université de Toulouse, CNRS, Toulouse, France
5 AIRBUS, Suresnes, France
6 DAMAS Labex, Université de Lorraine, France
Microstructural evolutions and resulting mechanical properties have been investigated in the near-β Ti-17 alloy following long- term ageing heat-treatment up to 6000 h at 450 °C. The initial microstructure was bimodal lamellar, consisting of two populations of α grains (αlam-primary and αsecondary) in a β phase matrix. Two microstructures were obtained either via controlled heat- treatments from the β phase field - in order to generate significant differences in the grain fraction, size, density and spatial distribution - or sampled from a part submitted to an industrial processing route. High energy XRD reveals that whatever the initial microstructure, the amount of α phase increases significantly after 1000 h long-term ageing. Complementary SEM and image analysis characterizations enable to deduce that this evolution is the consequence of αsecondary growth and/or coarsening. Also, TEM observations and EDX analysis show that the Mo and Cr contents of the β phase increase and that α2 nano-precipitates form within the αlam-primary grains. Considering the mechanical properties, long-term ageing leads to an increase in the yield and ultimate tensile strength, as well as a decrease in the elongation at failure, at an extent which depends on the ageing time.
Key words: near-β alloy / ageing / microstructure / crystallography / mechanical properties
© The Authors, published by EDP Sciences, 2020
This is an Open Access article distributed under the terms of the Creative Commons Attribution License 4.0, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.
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