Dresden 2006 – scientific programme
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MM: Metall- und Materialphysik
MM 8: Symposium Modern Metallic Materials Design II
MM 8.3: Talk
Monday, March 27, 2006, 15:15–15:30, IFW B
TEM investigations of TiAl-based intermetallic compounds — •Yong Yuan1, Zhi-Guo Liu1, Torben Boll2, and Talaat Al-Kassab2 — 1Laboratory of Solid State Microstructures, Nanjing University, Hankou Road 22, Nanjing 210093, China — 2Institut für Materialphysik der Universität Göttingen, Friedrich-Hund-Platz 1, 37077 Göttingen, Germany
TiAl based intermetallic alloys are promising high-temperature structural materials. Nb addition can enhance the strength, and precipitation hardening can improve the strength and creep-resistance of the alloys.
Dissociation of super-dislocations in Ti-48at.%Al-1at.%Nb and Ti-48at.%Al-10at.%Nb has been studied by HRTEM. Corresponding superlattice intrinsic stacking fault (SISF) energies in γ-TiAl were determined to be about 63 mJ/m2 and 34 mJ/m2, respectively. It is concluded that Nb addition can decrease the SISF energy, which may contribute to the strengthening effect. The microstructure of Ti-48 at.% Al-10 at.% Nb aged at 1073 K was also investigated by TEM. Needle-like γ1-Ti4Nb3Al9 precipitates in the γ-TiAl matrix predicted before were for the first time observed. Their morphology and the orientation relationship was characterized.
The precipitation reaction of L12-(Al,Ag)3Ti in an L10 -TiAl(Ag) based Ti-54at.%Al-2at.%Ag alloy has been studied by TEM, HRTEM and supporting micro-hardness test preliminarily. The maximum hardness appeared in the samples with an average precipitate diameter of about 40 nm. The morphological evolution of the precipitates was discussed.