Effect of addition of Mo and C on microstructure and properties of TiAl alloys with high Nb content

0449845 - ÚFM 2016 RIV CZ eng A - Abstract
Chlupová, Alice - Kruml, Tomáš - Heczko, Milan - Beran, Přemysl - Polák, Jaroslav
Effect of addition of Mo and C on microstructure and properties of TiAl alloys with high Nb content.
Book of Abstracts. 17th International Conference on the Strength of Materials (ICSMA-17). Brno: Ústav fyziky materiálů AV ČR, v. v. i., 2015 - (Dlouhý, A.; Kunz, L.). s. 49-49. ISBN 978-80-87434-07-9.
[ICSMA-17 International Conference on the Strength of Materials /17./. 09.08.2015-14.08.2015, Brno]
R&D Projects: GA ČR(CZ) GAP107/11/0704; GA MŠMT(CZ) ED1.1.00/02.0068
Institutional support: RVO:68081723 ; RVO:61389005
Keywords : titanium aluminides * microstructure * mechanical properties * electron microscopy * fatigue
Subject RIV: JL - Materials Fatigue, Friction Mechanics; BM - Solid Matter Physics ; Magnetism (UJF-V)

Six grades of TiAl alloy with 7% of Nb and doped with C and/or Mo were prepared. The effect of element addition on microstructure and phase composition was characterized using electron microscopy and neutron diffraction. The alloys had substantially different microstructure. Common feature of all materials were domains with alternating lamellae of γ and α2 phases. Presence of ordered β0 phase in the form of islands was observed in Mo containing alloys. The biggest amount of β0 phase evaluated using neutron diffraction was about 15% for material doped with 2% of Mo. Both SEM and TEM studies confirmed that in alloys containing carbon no β0 phase was observed. Microstructure of alloys with both Mo and C contained large islands of γ phase and small islands of β0 phase often connected to lamellae of γ and α2 phase. Monotonic properties were measured at ambient and elevated temperature. Tensile elongation of all alloys was rather limited at both temperatures however some materials exhibited reasonably good plasticity in compression at 750°C. The highest tensile strength was measured in the case of alloy doped with 0.5% C both at 750°C and RT. Results concerning ductility suggested that material with highest amount of β0 phase exhibited the highest values of plastic deformation at fracture. The differences in microstructure resulted also in differences in yield stress at 750°C, which varied from 443 to 628 MPa. Low cycle fatigue behavior was studied and cyclic stress-strain curve was assessed using short-cut procedure. Loading with low levels of applied strain amplitude resulted in a stable behavior or small cyclic hardening. Materials cycled with high strain amplitudes at 750°C exhibited initial cyclic softening. The highest cyclic stress-strain curve at RT had material doped with 0.5% C. The cyclic deformation characteristics of alloys doped with C and Mo at 750°C were similar, nevertheless, the highest cyclic stresses were measured for carbon containing material.
Permanent Link: http://hdl.handle.net/11104/0251269