Characterization of hot processing parameters of powder metallurgy TiAl-based alloy based on the activation energy map and processing map

Characterization of microstructure evolution in β-γ TiAl alloy containing high content of Niobium using constitutive equation and power dissipation map

“…The preferable condition is that the values of η increase with the increase of dissipative co-content, which indicates that more efficient microstructure evolution and lower risk of fracture failure. Mehtedi [38] reported that the values of η are calculated by combining the developed constitutive equation with the formula of η =2m/(m+ 1) that is based on the hypothetical condition of σ ¼ K _ ε m [25,28]. In the present study, the developed Arrhenius-type constitutive equations (Eqs.…”

“…The optimum hot working condition of strain rate and temperature is maximum value of J. The efficiency of power dissipation (J/J max ) is related to dynamic microstructural changes during hot deformation [28]. The variation of efficiency of power dissipation, as a dimensionless parameter, with strain, strain rate and deformation temperature constitutes power dissipation map [29].…”

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

“…Besides, according to Equation (1), the used value of Q in it is critical to the calculation accuracy of Z. As above described, the compression deformation under different parameters of present fine grained γ-TiAl alloy is related to a transition of deformation mechanism between dislocation creep and GBS, which leading to the inapplicability of the average value of Q under different deformation conditions other literatures commonly used [13][14][15][16][17] in the present work. In those literatures, the value of Q does not change with deformation parameters.…”

“…As we know, in the practical isothermal forging process, the deformation of the billet is mainly conducted under compressive stress state, and the deformation at different stages of the process and in different parts of the billet could be controlled by different mechanisms (i.e., dislocation creep versus grain boundary sliding (GBS)) corresponding to different deformation conditions (i.e., non-superplastic condition versus superplastic condition). 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.…”

Microstructure and high temperature mechanical properties of powder metallurgical Ti-45Al-7Nb-0.3W alloy sheets

“…Once the strain increased, there would be more dislocations and then subgrains could form, and the low-angle boundaries could turn into high-angle boundaries, then the dynamic recrystallization would occur. It has been claimed [33,34] that DRX is the main softening mechanism of TiAl alloy. It can absorb the strain energy and reduce the dislocation density to decrease the stress concentration.…”