In- and ex-situ study of the deformation behavior of the $β_{o}(ω_{o})$ phase in a Ti$_4$Al$_3$Nb alloy during high-temperature compression

Abstract

In-situ synchrotron-based high energy X-ray diffraction (HEXRD) and ex-situ Gleeble tests were conducted to investigate the deformation behavior of the $β_{o}(ω_{o})$ phase in a Ti$_4$Al$_3$Nb alloy. In samples compressed at 600 and 800 °C, the brittle $ω_o$ phase deforms mostly elastically, resulting in the failure of the Ti$_4$Al$_3$Nb alloy by premature fracture. In a sample deformed at 900 °C, the $ω_o$ phase mostly transforms into the $β_o$ phase under uniaxial loading. Moreover, the ductility of a Ti$_4$Al$_3$Nb alloy is largely enhanced at this temperature. In a sample deformed at 1000 °C, dynamic recrystallization (DRX) of the $β_o$ phase extensively takes place. Direction 1 (D1) and Direction 2 (D2) deviating from the loading direction with an angle of 65° ± 5° and 15° ± 5° are selected to analyze the lattice strain evolution of (110)$_{β_{o}}$ lattice planes. At the late stage of macro strain hardening, deformed $_{β_{o}}$//D1 oriented grains bear a higher load due to the occurrence of DRX in βo//D2 oriented grains. Subsequently, DRX continues in $_{β_{o}}$//D1 oriented $β_o$ grains. The coordinated deformation of $β_o$ grains ensures the good deformability of a Ti$_4$Al$_3$Nb alloy at 1000 °C