Influence of alloy composition and thermal history on carbide precipitation in γ-based TiAl alloys. (October 2017)

• Record Type: Journal Article
• Authors: Wang, Li; Lorenz, Uwe; Münch, Mathias; Stark, Andreas; Pyczak, Florian
• Is Part Of: Intermetallics. Volume 89(2017)
• Page Start: 32
• Page End: 39
• Publication Date: 2017-10
• Subjects: A. Intermetallics -- B. Alloy design -- B. Phase stability -- F. Diffraction/scattering (electron, neutron and X-ray) -- F. Electron microscopy -- Transmission; Intermetallic compounds -- Metallography -- Periodicals; Metallic glasses -- Periodicals; Composés intermétalliques -- Métallographie -- Périodiques; 669.94
• DOI: 10.1016/j.intermet.2017.05.006
• Languages: English
• ISSNs: 0966-9795

Abstract

Abstract: Carbide precipitation in TiAl alloys with different alloying element additions and thermal history was investigated by transmission electron microscopy and high energy X-ray diffraction. The results reveal that Nb addition in TiAl alloys does not increase the carbon solubility in the γ matrix significantly. With increasing carbon concentration in the alloys, a splitting of the P-type carbides takes place earlier in the course of ageing at 800 °C and the formation of H-type carbides is promoted. For a nearly single γ phase alloy Ti51Al5Nb0.5C, H-type carbides are the thermodynamically stable phase. However, with decreasing Al concentration, P-type carbides become thermodynamically stable at low carbon concentration (below 1%) in Ti45Al and Ti45Al5Nb alloys. It is feasible to achieve high thermodynamical stability of the P-type carbides in TiAl alloys through controlling alloying elements. Highlights: Nb does not increase the carbon solubility in the γ phase significantly. A higher carbon content leads to an earlier splitting of the P-type carbides and promotes the formation of H-type carbides. A high thermodynamic stability of the P-type carbides in TiAl alloys can be achieved by controlling alloying elements.