Characterization of the elevated temperature compressive deformation behavior of high Nb containing TiAl alloys with two microstructures

Microstructure Evolution of a High Nb Containing TiAl Alloy with (α2 + γ) Microstructure during Elevated Temperature Deformation

“…In order to keep the deformation and temperature distribution throughout specimens being uniform, some specific methods and measures were applied in the compression tests, detailed in Ref. [24].…”

“…In previous works [23,24], based on the strain rate dependence of flow stress (the double logarithmic relationship between shear modulus compensated peak stress (σ/G) and diffusion compensated strain rate ( . ε/D L ) under different deformation conditions as shown in Figure 2 in Ref.…”

“…[23] and in Figure 6 in Ref. [24], the compression parameters (950-1050 • C and 10 −2 s −1 -10 −4 s −1 ) can be divided into three categories with increasing temperatures and decreasing strain rates: dislocation creep region, transition region and GBS region. Correspondingly, when the specimens deformed at parameters in dislocation creep region, the compression deformation is dominated by dislocation creep mechanism and fulfilled mainly through intragranular dislocation sliding and climbing in γ grains.…”

“…In those literatures, the value of Q does not change with deformation parameters. Therefore, the varied Combining with the preliminary flow curves analysis and microstructure characterization via SEM in BSE mode in previous works [23,24] and the above detailed microstructure characterization via EBSD in the present work, it can be therefore concluded that γ phase DRX takes place during the compression deformations throughout the whole conditions whether non-superplastic dislocation creep mechanism dominated (e.g., 1000 • C/10 −2 s −1 ) or superplastic GBS mechanism dominated (e.g., 1050 • C/10 −4 s −1 ). The recrystallized γ grain size decreases with the increasing strain rate and decreasing deformation temperature ( Figure 2).…”

“…However, the pioneering research works regarding isothermal compression deformation of γ-TiAl alloys [13][14][15][16][17] and superplasticity of γ-TiAl alloys via tension deformation [18][19][20][21][22] rarely involve the above issues. Therefore, in previous works [23,24] a deformation mechanism transition from dislocation creep to GBS with increasing deformation temperature and decreasing strain rate was revealed via the investigation of the isothermal compression of a fine-grained high Nb containing TiAl alloy with a (α 2 + γ) microstructure. The results of flow behavior analysis and preliminary microstructure characterization suggested that dislocation creep and GBS contribute independently and additively to the strain rate.…”