In situ study of phase transformations in electron beam additive manufactured Ti-6Al-4 V titanium alloy by high temperature synchrotron X-ray diffraction and TEM

• Published in: Journal of alloys and compounds 2022-10, Vol.917, p.165463, Article 165463
• Main Authors: Perevalova, O.B., Syrtanov, M.S.
• Format: Article
• Language: English
• Subjects: Beta phase; Crystal lattices; Electron beam additive manufacturing; Electron beams; Heat resistant alloys; Heating; High temperature; Lattice parameters; Microstructure; Phase composition; Phase transformation α→α; Phase transitions; Phase volume fraction; Room temperature; Synchrotron radiation; Synchrotrons; Ti-6Al-4 V; Titanium alloys; Titanium base alloys; Transmission electron microscopy; Vanadium; X-ray diffraction
• ISSN: 0925-8388; 1873-4669
• DOI: 10.1016/j.jallcom.2022.165463

The microstructure and phase composition of the EBAM Ti-6Al-4 V alloy samples were studied by the methods of in situ high temperature synchrotron X-ray diffraction and transmission electron microscopy (TEM) during heating from room temperature to a temperature of 1373 K. In the initial state, the main phase of the EBAM Ti-6Al-4 V alloy the samples was the α phase, the second phases were β + α″. The volume fraction of the β phase does not exceed 5%, α″ - 3%. It was found that the new α″ phase was formed at the temperature of 1073 K due to the phase transition α→α″. The α″ phase volume fraction increased as the heating temperature increased to the temperature of 1223 K and then decreased with a further increase of the temperature due to the α″→β phase transition. The dependences of the lattice parameters of the α, β and α″ phases on the heating temperature were revealed. It was established that the crystal lattice of the α phase was distorted during heating. The α phase passed into the unstable state. An increase of the c/a parameters ratio was accompanied by the formation of the α″ and β phases. Heating temperatures: 303 K (a), 873 K (b), 1073 K(c), Temperature 1173 K. 1223 K (d), 1323 K (e), 1373 K (f). [Display omitted] •Investigation of a phase transformations in the 3D-printing Ti-6Al-4 V titanium alloy during heating. At a temperature of 1073K the phase transformation α → α ″ occurs in individual lamellar α grains with low-angle boundaries. With an increase in temperature the volume fraction of the α ″ phase increases and at 1223 K it reaches the maximum value. With increase in temperature up to 1373K the α ″ phase volume fraction decreases due to the phase transformation α.″ → β. An increase in c/a is accompanied by the formation of the α ″ and β phases.