Study on Fracture Mechanisms of TiAl Alloys by In Situ Tensile Tests |
| Journal |
Key Engineering Materials (Volumes 353 - 358) |
| Volume |
Progresses in Fracture and Strength of Materials and Structures |
| Edited by |
Yu Zhou, Shan-Tung Tu and Xishan Xie |
| Pages |
34-37 |
| DOI |
10.4028/www.scientific.net/KEM.353-358.34 |
| Online since |
September, 2007 |
| Authors |
Rui Cao,
Jian Hong Chen,
J. Zhang
|
| Keywords |
Fracture Mechanism, Fracture Process, TiAl Alloy |
| Abstract |
Combining in-situ tensile tests with detailed observations of fracture surfaces of a
two-phase TiAl alloy, the fracture process and fracture mechanisms of TiAl alloys are investigated.
The results reveal that Cracks prefer to initiate and propagate along lamellar interfaces, which are
the weakest link in the near fully lamellar microstructure. The interlamellar strength calculated is
less than the translamellar strength. The tensile stress is the driving force for crack initiation and
propagation. In specimens with a slit notch, most cracks are initiated directly from the notch root
and extended along lamellar interfaces. The main crack can be stopped or deflected into a
delamination mode by a barrier grain with a lamellar interface orientation deviated from the
direction of crack propagation. In this case, new cracks are nucleated along lamellar interfaces of
grains with favorable orientation ahead the barrier grain. The main crack and a new crack are then
linked by the translamellar cleavage fracture of the barrier grain with increasing applied load. In
order to extend the main crack, further increases of the applied load are needed to move the high
stress region into the ligament until final fracture. The process of a new crack nucleation with a
bridging ligament formation decreases the crack propagation resistance rather than increases it. |
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