1. The interaction of borides and longitudinal twinning in polycrystalline TiAl alloys.
- Author
-
Edwards, Thomas Edward James, Di Gioacchino, Fabio, Muñoz-Moreno, Rocío, and Clegg, William John
- Subjects
- *
BORIDES , *TWINNING (Crystallography) , *POLYCRYSTALS , *TITANIUM-aluminum alloys , *TEMPERATURE effect - Abstract
In this paper the occurrence of twinning parallel to the lamellae during compression at 700 °C of a polycrystalline nearly lamellar commercial γ-TiAl alloy, Ti-45Al-2Nb-2Mn(at%)-0.8 vol% TiB 2 , has been studied and shown to lead to the formation of cracks at colony boundaries. However, the occurrence of this longitudinal twinning mode was less common by at least a factor of ten in tests at room temperature. Furthermore, the debonding of colony boundaries caused by the shear strain of longitudinal twinning is exacerbated when the same γ-TiAl variant favourably oriented for twinning occurs repeatedly in the lamellar structure. This effect was caused by the preferential nucleation of certain γ-TiAl variants in the presence of TiB 2 boride reinforcement. It is shown that the boride additions increase the probability of double, triple or even higher order multiply stacked γ-variants. This increases the resulting shear strain that must be accommodated and hence the probability of crack nucleation. [ABSTRACT FROM AUTHOR]
- Published
- 2017
- Full Text
- View/download PDF