Can local hot spots induce α2/γ lamellae during incomplete massive transformation of γ-TiAl alloys?

Fischer, Franz Dieter; Cha, Limei; Dehm, Gerhard; Clemens, Helmut

doi:10.1016/j.intermet.2010.01.017

Cited by 7 publications

(4 citation statements)

References 29 publications

(42 reference statements)

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“…On the one hand, different cooling rates lead to different phase constitutions of the prealloyed powders with different sizes, and α phase transforms into γ m phase (massive γ phase) in coarse powders due to a relatively low cooling rate [35]. During the subsequent densification process, the specific strain of γ m phase is generated due to lattice distortion, which provides a driving force for subsequent grain growth and full lamination [36]. On the other hand, segregation during solidification leads to the reduction in or disappearance of the α phase in local regions, resulting in γ-phase coarsening without the pinning effect of the α phase during subsequent densification [37].…”

Section: Microstructural Evolutionmentioning

confidence: 99%

Evolution Behavior of Rapidly Solidified Microstructure of a Ti-48Al-3Nb-1.5Ta Alloy Powder during Hot Isostatic Pressing

Zuo

et al. 2023

Metals

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In this study, Ti-48Al-3Nb-1.5Ta powders were manufactured from cast bars by the supreme-speed plasma rotating electrode process (SS-PREP) and used to prepare hot isostatically pressed (HIPed) material at 1050–1260 °C with 150 MPa for 4 h. The phase, microstructure and mechanical performance were analyzed by XRD, SEM, electrical universal material testing machine and other methods. The results revealed that the phase constitution changed from γ phase to α2 phase and then to γ phase with the material changing from as-cast to powders and then to as-HIPed. Compared with the as-cast material, the grain size and element segregation were significantly reduced for both powders and as-HIPed. When the hot isostatic pressing (HIP) temperature was low, the genetic characteristics of the powder microstructure were evident. With the HIP temperature increasing, the homogeneity of the composition and microstructure increased, and the prior particle boundaries (PPBs) gradually disappeared. The elastic moduli of powder and as-HIPed were superior to those of as-cast, which increased with the HIP temperature increasing. The hardness of as-HIPed was lower than that of the powder. The compressive strength, compressive strain, bending strength, and tensile strength of as-HIPed were higher than those of as-cast. With an increase in the HIP temperature, the compressive strength decreased gradually, and the compressive strain first decreased and then increased.

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Section: Microstructural Evolutionmentioning

confidence: 99%

Evolution Behavior of Rapidly Solidified Microstructure of a Ti-48Al-3Nb-1.5Ta Alloy Powder during Hot Isostatic Pressing

Zuo

et al. 2023

Metals

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“…Recent experiments, e.g., as those by Hu et al [8], and according computational studies as the molecular dynamics simulations by Wu et al [9] and numerical studies by Steinmann and cooperators [10] have brought out that a so-called Kapitza interface is a satisfying physical representation, enforcing that the jump of the temperature at the interface must be proportional to the continuous heat flux across the interface. The second problem concerns the time evolution of the temperature profile in the particle and in the surrounding, e.g., with the aspect of the so-called autocatalytic effects (i.e., generation of second phases due to the local heating or cooling, see, e.g., [11]). This paper is devoted to the second problem, providing new mathematical tools to find analytical expressions for the temperature profiles.…”

Section: The Hot Spot and Precipitation Problemmentioning

confidence: 99%

Generalized Gaussian error functions and their applications

Dirschmid

Fischer

2015

Acta Mech

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The Gaussian error functions play a significant role in analytical solutions for problems of thermomechanics and mass flow due to diffusion. These functions are extended to a family of generalized Gaussian error functions with an infinite number of members. The use of this new family of functions allows finding analytical solutions in form of absolutely converging series for a much wider class of problems compared to available analytical solutions. The Laplace transformation is an established tool to handle time-dependent problems. It is outlined in detail, how the generalized Gaussian error functions can be efficiently used for the inversion of the solution from the Laplace transform domain to the original domain by the extension of the so-called correspondence relation. As example, an analytical solution for the heat conduction from an inclusion into the outer space with material properties different to those of the inclusion is demonstrated.

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“…However, the addition of B suppresses the formation of the massive γ phase and increases the tendency of lamellar structure formation by the refinement of the high-temperature α phase, whereas the cooling rated needed for the onset of massive γ formation is hardly changed [18]. The massive γ phase is commonly reported to nucleate at the grain boundaries during cooling [9,19,20], which means that a fine-grained initial microstructure can facilitate the massive γ formation. Actually, the volume fraction of the massive γ phase depends on the specialized window of cooling rates for each alloy.…”

Section: Introductionmentioning

confidence: 99%

Microstructure Evolution of a Ti-45Al-8.5Nb-0.2W-0.2B-0.02Y Alloy during Massive Transformation and Subsequent Annealing

Song

Wang

Xue

et al. 2018

Metals

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It has been widely reported that the microstructure refinement of TiAl alloys can be achieved by massive transformation and subsequent annealing in α 2 + γ two phase field. To achieve this goal, several heat treatment parameters must be adjusted, including the heat treatment temperature around single α phase field, the annealing temperature, and the annealing time for the precipitation of α 2 phase. Thus, a systematic study is needed for each alloy with different compositions. In this study, the heat treatment parameters for grain refinement via massive transformation of a high Nb-containing TiAl are investigated. Precipitation of α 2 phase during annealing is observed by transmission electron microscopy. It is found that 30 min at single α phase field is appropriate for the massive transformation; a full, massively transformed microstructure cannot be obtained by oil or water quenching. A short annealing time can result in a refined microstructure, whereas the sizes of the precipitated α 2 phase increases with the increase of annealing time. The α 2 phase can form at the interface of twin boundaries of the γ phase, following the Blackburn orientation relationship with both sides. The Vickers hardness is measured for the annealed samples, which remains relatively stable for different annealing times.

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Can local hot spots induce α2/γ lamellae during incomplete massive transformation of γ-TiAl alloys?

Cited by 7 publications

References 29 publications

Evolution Behavior of Rapidly Solidified Microstructure of a Ti-48Al-3Nb-1.5Ta Alloy Powder during Hot Isostatic Pressing

Evolution Behavior of Rapidly Solidified Microstructure of a Ti-48Al-3Nb-1.5Ta Alloy Powder during Hot Isostatic Pressing

Generalized Gaussian error functions and their applications

Microstructure Evolution of a Ti-45Al-8.5Nb-0.2W-0.2B-0.02Y Alloy during Massive Transformation and Subsequent Annealing

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