Precipitation processes in the Beta-Titanium alloy Ti-5Al-5Mo-5V-3Cr

JOURNAL OF ALLOYS AND COMPOUNDS

卷:646

Article

Coakley, James^1,2  Vorontsov, Vassili A.³  Jones, Nicholas G.¹  Radecka, Anna³  Bagot, Paul A. J.⁴  Littrell, Kenneth C.⁵  Heenan, Richard K.⁶  Hu, Frederic³  Magyar, Andrew P.⁷  Bell, David C.⁷  Dye, David³ 

[1] Univ Cambridge, Dept Mat Sci & Met, Cambridge CB3 OF3, England

[2] Northwestern Univ, Dept Mat Sci & Engn, Evanston, IL 60208 USA

[3] Univ London Imperial Coll Sci Technol & Med, Dept Mat, London SW7 2AZ, England

[4] Univ Oxford, Dept Mat, Oxford OX1 3PH, England

[5] Oak Ridge Natl Lab, Chem & Engn Mat Div, Oak Ridge, TN 37831 USA

[6] Rutherford Appleton Lab, Didcot OX11 0QX, Oxon, England

[7] Harvard Univ, Sch Engn & Appl Sci, Cambridge, MA 02138 USA

关键词: Precipitation;    Titanium alloys;    Atom probe tomography (APT);    Transmission electron microscopy (TEM);    Small angle neutron scattering (SANS);   

DOI  :  10.1016/j.jallcom.2015.05.251

来源: Elsevier

【 摘 要 】

Precipitate evolution in Ti-5Al-5Mo-5V-3Cr-0.3Fe wt.% (Ti-5553) has been studied in-situ by small angle neutron scattering (SANS) during a two step ageing heat treatment of 300 degrees C/8h+500 degrees C/2 h. The first heat treatment step precipitates omega, with a corresponding increase in hardness of similar to 15% compared to quenched material. The second heat treatment step precipitates fine scale alpha from the omega phase, with a similar to 90% increase in hardness compared to quenched material. The SANS measurements are complemented by atom probe tomography (APT) to give compositional information, ex-situ transmission electron microscopy (TEM) to confirm phase identification and size distribution locally, and X-ray diffraction (XRD) for additional confirmation of phase identification. The omega phase is depleted in all the solute additions following 300 degrees C/8 h ageing heat treatment. The volume fraction of the omega phase from APT is estimated to be similar to 7%. SANS modelling is consistent with disc shaped particles for the omega phase. The mean particle diameter increases from similar to 7.5 nm to 9.5 nm diameter between 1 h and 8 h heat treatment at 300 degrees C, while the thickness increases from similar to 4 nm to similar to 5 nm. The SANS model estimates the volume fraction to be similar to 10% for the 8 h heat treatment, using the phase compositions from APT. (C) 2015 Elsevier B.V. All rights reserved.

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