Grain-boundary sliding in a TiAl alloy with fine-grained duplex microstructure during 750 degrees C creep
D. Peter, G. B. Viswanathan, M. F. Wagner, G. Eggeler.
Materials Science and Engineering A -Structural Materials Properties Microstructure and Processing, Elsevier Science SA, PO BOX 564, 1001 Lausanne, Switzerland, 510-11, 359-363, (2009)
Constant-load creep experiments at a temperature of 750 degrees C and a nominal stress of 300MPa were conducted on a fine-grained Ti-45Al-5Nb-0.2B-02C (in at.%) alloy with a duplex microstructure. Microstructures before and after creep (accumulated strain: 9.6%) were analyzed using scanning and transmission electron microscopy (SEM and TEM). TEM analysis after creep indicates that the individual microstructural constituents of the fine duplex microstructure, namely, the equiaxed gamma and the lamellar alpha(2)/gamma colonies, undergo varying degrees of deformation and develop various substructures. Lamellar grains deform by dislocation creep. They show clear evidence for dislocation and twin activity. In contrast, only few dislocations are found in the equiaxed grains. We show that the regions with small equiaxed gamma grains, representing 65-75 vol.% of the microstructure, deform by grain-boundary sliding.
Keyword(s): gamma titanium aluminide; fine-grained duplex microstructure; creep; grain-boundary sliding