Chemical heterogeneities in tungsten containing TiAl alloys processed by powder metallurgy

Couret, Alain; Allen, Melissa; Rackel, Marcus Willi; Galy, Benjamin; Monchoux, Jean‐Philippe; Güther, Volker; Pyczak, Florian; Sallot, Pierre; Thomas, Marc

doi:10.1016/j.mtla.2021.101147

Cited by 11 publications

(5 citation statements)

References 14 publications

(21 reference statements)

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“…However, certain β-stabilizing elements, e.g., W, are prone to pronounced segregations upon solidification, because of their low diffusivity and distinct partitioning behavior. [6,114] The most prominent feature of the system shown in Figure 6a and generally most systems with sufficient amounts of β-stabilizing elements, though, is the presence of an ordered B2 phase at low temperatures when compared to the binary Ti-Al system. This so-called β o phase, whose crystal structure is depicted in Figure 6b, corresponds to the ordered counterpart of the high-temperature β phase.…”

Section: β-Stabilizing Elementsmentioning

confidence: 99%

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Alloying Elements in Intermetallic γ‐TiAl Based Alloys – A Review on Their Influence on Phase Equilibria and Phase Transformations

et al. 2023

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Intermetallic γ–TiAl based alloys are innovative structural materials dedicated to applications in the automotive and aeronautic industry. Especially their low density, high specific yield strength and excellent resistance against creep and oxidation make them a suitable choice for structural high‐temperature components in combustion engines. However, further improvement of their properties and processability is required to conquer new application areas and facilitate cost‐effective production. While the incorporation of additional alloying elements is a promising possibility, their effects on the phase transformations and phase equilibria need to be considered rigorously. In this context, this review provides a detailed survey of the research work on the influence of technically important alloying elements on the Ti–Al phase diagram. First, an introduction to the fundamentals of the phase transformations in γ‐TiAl based alloys and the consequences of changed cooling conditions, relevant for example to the latest developments within the field of processing, is given. Afterwards, the alloying elements, categorized with respect to their stabilization effect, are discussed and their particularities highlighted. Topics covered include established ternary phase diagrams and isoplethal sections, the stabilization of additional phases as well as the influence of alloying elements on the microstructure of modern engineering intermetallic γ‐TiAl based alloys.This article is protected by copyright. All rights reserved.

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Section: β-Stabilizing Elementsmentioning

confidence: 99%

“…However, certain β‐stabilizing elements, e.g., W, are prone to pronounced segregations upon solidification, because of their low diffusivity and distinct partitioning behavior. [ 6,114 ]…”

Section: Effect Of Additional Alloying Elements On the Phase Transfor...mentioning

confidence: 99%

Alloying Elements in Intermetallic γ‐TiAl Based Alloys – A Review on Their Influence on Phase Equilibria and Phase Transformations

et al. 2023

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“…This study demonstrates the critical role that powder quality plays in producing SPS materials with high mechanical properties. In addition, a recent study of W segregations has shown the impact of the initial ingot quality for that of the final SPS product [40].…”

Section: Plasticity and Brittleness Of The As-spsed Tnm + Alloymentioning

confidence: 99%

Microstructure, Plasticity and Ductility of a TNM+ Alloy Densified by Spark Plasma Sintering

Musi

Deshayes

Molenat

et al. 2022

Metals

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This work presents a study of the microstructure and mechanical properties of a TNM+ alloy (Ti-43.5Al-4Nb-1Mo-0.1B-0.3C-0.3Si, in at.%) densified by Spark Plasma Sintering (SPS), in comparison to the as-SPSed TNM alloy, which contains neither carbon nor silicon. Tensile tests at room temperature and 800 °C, as well as creep tests at 800 °C and 200 MPa, were performed. The microstructures and the fracture surfaces of deformed samples were studied by scanning and transmission electron microscopies, as well as by X-ray diffraction. The deformation mechanisms were investigated by means of in situ straining experiments and post-mortem analyses of deformed samples, both performed by transmission electron microscopy. Contrary to the TNM alloy, the as-SPSed microstructure of the TNM+ alloy does not contain β/βo phase due to the incorporation of carbon. At room temperature, the TNM+ alloy exhibits a yield stress of 520 MPa but a poor ductility of less than 0.1% of plastic strain. The incorporation of carbon and silicon leads to an increase in the creep resistance of the alloy at 800 °C. Despite the fact that iron inclusions are responsible for the premature failure of some samples during tensile tests, the TNM+ alloy is found to be able to deform plastically at room temperature by the glide of ordinary dislocations and by twinning.

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“…[8,10] Especially, the highly nonequilibrium phase distribution and microstructure of the powder arising from extremely high cooling rate of the gas atomization the gas atomization as well as the resulting distribution of slowly diffusing elements can have a substantial impact on the observed phase transformations and the final microstructure when compared to thermodynamic equilibrium. [14,15] In this context, the current work presents a detailed study on the transformation of such a nonequilibrium material condition toward thermodynamic equilibrium in a W-containing γ-TiAl based powder, which was produced by means of electrode induction melting gas atomization (EIGA). The chemical composition of this model alloy, i.e., Ti-46.3Al-2.2W-0.2B (at%), allows to close some gaps in the knowledge of the phase transformation behavior in the Ti-Al-W system, for which only a few studies are available in the literature, especially when compared to Nb-and Mo-containing alloys.…”

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

On the Temperature‐Induced Equilibration of Phase Distribution and Microstructure in a Gas‐Atomized Titanium Aluminide Powder

et al. 2022

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Powder production by gas atomization of γ‐TiAl based alloys typically yields a highly nonequilibrium material regarding the occurring phases and their microstructural appearance. In particular, the equilibration of the powder and the associated phase transformations during heating are of great importance for the subsequently applied densification techniques. The present work employs in situ high‐energy X‐ray diffraction to investigate how this thermodynamic equilibration manifests itself in the resulting phase distribution, the ordering behavior of the disordered α and β phase, both evidenced in the powder, and the change of the γ lattice parameters during heating of a Ti–46.3Al–2.2W–0.2B (at%) powder up to 850 °C. Complementary microstructural characterization of the gas‐atomized powder and the heat‐treated material condition reveals that the temperature exposure predominately affects the dendritic parts of the microstructure, especially when the α phase is transformed into γ phase with small embedded grains of α2 and βo.

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Chemical heterogeneities in tungsten containing TiAl alloys processed by powder metallurgy

Cited by 11 publications

References 14 publications

Alloying Elements in Intermetallic γ‐TiAl Based Alloys – A Review on Their Influence on Phase Equilibria and Phase Transformations

Alloying Elements in Intermetallic γ‐TiAl Based Alloys – A Review on Their Influence on Phase Equilibria and Phase Transformations

Microstructure, Plasticity and Ductility of a TNM+ Alloy Densified by Spark Plasma Sintering

On the Temperature‐Induced Equilibration of Phase Distribution and Microstructure in a Gas‐Atomized Titanium Aluminide Powder

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