Microstructural evolution and tensile behavior of Ti2AlNb alloys based α2-phase decomposition

The formation mechanism of the fine plate-like O-phases within alpha(2-)phases and tensile behavior of an isothermally forged Ti-22Al-25Nb (at%) orthorhombic alloy at 1040 degrees C during heat treatment were investigated. The investigation indicated that the alloys were heat-treated in O+B2 phase region after alpha(2)+ B2 phase region isothermally forging, the equiaxed alpha(2)-phase was not stable and decomposed into O+alpha(2) phases. The alpha(2) phases formed during isothermal forging process have higher concentration of Nb and begun to decompose during O+B2 phase region heat treatment. And then the alpha(2) phases separated into Niobium-lean and Niobium-rich regions through the Niobium diffusion: alpha(2)->alpha(2) (Nb-lean)+ O (Nb-rich). Nb-rich regions with composition similar to Ti2AlNb transformed to the O-phase, while the Nb-lean regions remained untransformed and retained the alpha(2)-phase. The deformation behavior and fracture mechanism of Ti-22Al-25Nb alloy at room temperature were discussed. The deformation behavior and microstructural evolution of this alloy at different temperatures and stain rates were also investigated using uniaxial tensile test. (C) 2016 Elsevier B.V. All rights reserved.