Temperature dependence of superdislocation core configurations in single crystal L1{sub 0} Ti-Al-V alloys. Ph.D. Thesis

Thesis/Dissertation · Sat Dec 31 04:00:00 EST 1994

OSTI ID:147184

Li, Z

Single crystals of L1{sub 0} type Ti44Al54V2 alloys were deformed to 0.6-0.8 percent under uniaxial compression at room temperature, 573, 673, 873, and 1073 K. The dissociated configurations of superdislocations (b = (011)) in the deformed alloys have been studied under weak beam conditions in order to determine the temperature dependence of the configurations and their correlation with deformation behaviors. The study showed that the dissociated configurations remained coplanar in the intermediate temperature regime (300-673 K), but became nonplanar at the high temperature regime (875-1073 K), in which one of the two superpartials and the APB cross-slipped onto a cube plane (K-W configuration). This indicates that a K-W mechanism becomes operational at the high temperature regime. In contrast, in the intermediate temperature regime, the superdislocations often cross-slipped onto other octahedral plane, or decomposed into two perfect dislocations (b = 1/2 less than 112) and b = 1/2 less than bar 110 thereby forming faulted dipoles. These faulted dipoles have not been observed in the single crystals of Ti-Al-V alloys deformed in the high temperature regime (873-1073 K), where the K-W configurations are a dominant mode in this temperature regime. This suggests that the cross-slip was aided by sufficient thermal energy necessary to overcome the energy barrier in this temperature regime. In addition to the K-W configurations in the high temperature regime, the superkinks also formed. This implies that the superkinks may play an important role in the deformation of this material. The apparent activation energy for the cross-slip of APB`s onto the cube plane was found to be 0.058 eV in the high temperature regime. Based on the temperature dependence of deformation and dislocation core configurations in this alloy, it is proposed that two different deformation mechanisms with different activation energies operate in the two different temperature regimes.

• Research Organization: Polytechnic Univ., Brooklyn, NY (United States)
• OSTI ID: 147184
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
ACTIVATION ENERGY
ALUMINIUM ALLOYS
DEFORMATION
DISLOCATIONS
MONOCRYSTALS
TEMPERATURE DEPENDENCE
TEMPERATURE RANGE 0273-0400 K
TEMPERATURE RANGE 0400-1000 K
TEMPERATURE RANGE 1000-4000 K
TITANIUM ALLOYS
VANADIUM ALLOYS