Instability of the O-phase in Ti–22Al–25Nb alloy during elevated-temperature deformation

• Published in: Journal of alloys and compounds 2013-11, Vol.578, p.96-102
• Main Authors: Lin, Peng, He, Zhubin, Yuan, Shijian, Shen, Jun, Huang, Yongjiang, Liang, Xiaobo
• Format: Article
• Language: English
• Subjects: Alloy systems; Coarsening; Condensed matter: structure, mechanical and thermal properties; Deformation and plasticity (including yield, ductility, and superplasticity); Exact sciences and technology; Fragmentation; Instability; Mechanical and acoustical properties of condensed matter; Mechanical properties of solids; Microstructural instability; Microstructure; Physics; Softening; Spheroidization; Stability; Strain; Tensile deformation; Ti2AlNb; Titanium base alloys
• ISSN: 0925-8388; 1873-4669
• DOI: 10.1016/j.jallcom.2013.05.018

•Instability of the O-phase was enhanced by the elevated-temperature deformation.•The strain enhanced the instability of the O-phase more than the applied stress.•After ε=0.56, a refined microstructure with near-equiaxed O-phase grains formed.•The flow softening resulted from the transition of the deformation mode. The deformation behavior and microstructural evolution of a Ti–22Al–25Nb alloy during tensile deformation at 900°C was systematically investigated. The true stress–strain curve exhibited an initial hardening transient, a peak flow stress, and then a flow softening. The alloy exhibited a microstructural instability during the tensile deformation, characterized by coarsening, fragmentation, and spheroidization of the O-phase. This microstructural instability was enhanced by the imposed strain rather than the applied stress. After a strain of ε=0.56, a refined microstructure with equiaxed or near-equiaxed O-phase grains formed. Based on the results of the microstructural evolution, the origin of the flow softening behavior was suggested.