Tracking the αʺ martensite decomposition during continuous heating of a Ti-6Al-6V-2Sn alloy

Barriobero-Vila, Pere; Oliveira, Verona Biancardi; Schwarz, Sabine; Buslaps, T.; Requena, Guillermo

doi:10.1016/j.actamat.2017.06.018

Cited by 55 publications

(25 citation statements)

References 37 publications

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“…Figure 4 shows the relationship between R e/a and the martensitic transformation temperature in the sample with Gd doping. Whereas, the R e/a value can be evaluated by Equation (2) [19]:…”

Section: Discussion On Martensite Transition With Ga Dopingmentioning

confidence: 99%

“…In previous studies, the martensite transformation process in Ti [18][19][20] and Fe [21] alloys had been clear, but in Co-Ni-Al FSMAs, a low martensite transformation temperature has still restricted its industrial applications. For another, doping magnetic rare elements in FSMAs, i.e., Dy [16,22], Tb [23], Nd [24], or Gd [25,26], can significantly affect the microstructure variation and phase transition temperature.…”

Section: Introductionmentioning

confidence: 99%

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Martensite Transformation and Mechanical Properties of Polycrystalline Co-Ni-Al Alloys with Gd Doping

Liu

Shuai

et al. 2018

Metals

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In order to improve the mechanical properties and phase transition temperature, the influence of Gd doping on the microstructure, phase transition temperature and mechanical properties of Co35Ni32Al33 alloy was investigated. The results show that the γ+β phase was observed in the microstructure of the sample with less Gd doping and the γ phase+martensite was found with more Gd content. The phase transition temperature apparently increases with Gd doping and the phase transition temperature goes over room temperature when the Gd is 3 at.% or more. With increasing Gd doping, more γ phase appears in the sample which results in decrease in hardness. The compressive strength decreases from 2274 to 1630 MPa and the ductility increase from 4.2 to 12.9% with increasing Gd content.

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“…Figure 4 shows the relationship between R e/a and the martensitic transformation temperature in the sample with Gd doping. Whereas, the R e/a value can be evaluated by Equation (2) [19]:…”

Section: Discussion On Martensite Transition With Ga Dopingmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Martensite Transformation and Mechanical Properties of Polycrystalline Co-Ni-Al Alloys with Gd Doping

Liu

Shuai

et al. 2018

Metals

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“…In this way Nb depleted (α″ lean ) and Nb enriched (α″ rich ) domains form, which evolve continuously into equilibrium α and β phases. Interestingly, even though conceptualized for the first time more than 35 years ago 10,39,43 , α″ decomposition has only recently come into focus 8,9,44,45 . Its investigation has benefited significantly from the use of high temperature in-situ diffraction set-ups at synchrotron facilities 8,9 , similarly to the study of α″ iso .…”

mentioning

confidence: 99%

“…Interestingly, even though conceptualized for the first time more than 35 years ago 10,39,43 , α″ decomposition has only recently come into focus 8,9,44,45 . Its investigation has benefited significantly from the use of high temperature in-situ diffraction set-ups at synchrotron facilities 8,9 , similarly to the study of α″ iso . Most notably, while ex-situ XRD in earlier work struggled to detect variations of the α″ lean lattice parameters with holding time 25 , in-situ measurements clearly revealed their evolution towards α 9 .…”

mentioning

confidence: 99%

“…In recent experiments it was possible to detect and follow these transitional structures in binary Ti-Nb in-situ by www.nature.com/scientificreports www.nature.com/scientificreports/ high temperature XRD 9 . By now, transitional orthorhombic phases have been observed in several β-stabilized Ti-alloys including a few commercially important formulations [7][8][9][10][11] . Informed by the energy landscape and the experimental evidence 9 we reinterpret the heat flow signatures of 9-19 at% Nb alloys recorded by DSC (Figs.…”

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confidence: 99%

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Routes to control diffusive pathways and thermal expansion in Ti-alloys

Bönisch

Stoica

Calin

2020

Sci Rep

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β-stabilized Ti-alloys present several unexplored and intriguing surprises in relation to orthorhombic α″ phases. Among them are (i) the diffusion-controlled formation of transitional α″ iso , α″ lean and α″ rich phases and ii) the highly anisotropic thermal expansion of martensitic α″. Using the prototypical Ti-Nb system, we demonstrate that the thermodynamic energy landscape reveals formation pathways for the diffusional forms of α″ and may lead to a stable β-phase miscibility gap. In this way, we derive temperature-composition criteria for the occurrence of α″ iso and resolve reaction sequences during thermal cycling. Moreover, we show that the thermal expansion anisotropy of martensitic α″ gives rise to directions of zero thermal strain depending on Nb content. Utilizing this knowledge, we propose processing routes to achieve null linear expansion in α″ containing Ti-alloys. These concepts are expected to be transferable to other Ti-alloys and offer new avenues for their tailoring and technological exploitation. β-stabilized Ti-alloys provide the basis for a multitude of future applications in biomedicine and aeronautics 1,2. Their low elastic moduli, shape memory and superelastic effects, blended with pronounced hardenability and attractive ductility captivates the attention of engineers and material scientists alike. Despite their seemingly simple phase diagrams β-stabilized systems, such as Ti-Nb (Fig. 1) show a vast array of phase transformations and transient states, attributed to the extensive α-β two-phase field. The ensuing exceptionally pronounced metastability necessitates large diffusional compositional changes and extended aging durations (up to many weeks or months) to reach (meta)stable equilibrium. The nature of compositional fluctuations decisively influences the refinement of precipitation products 3-5 and the β ↔ α″ martensitic transformation 6. For instance, detailed (micro)structural studies uncovered non-conventional transformation pathways for α-precipitation 3,7-9. Of particular note is the discovery of transitional α″-like structures (α″ iso , α″ lean , α″ rich) during martensite decomposition and prior to α precipitation 7-11. Furthermore, recently extraordinarily large anisotropic thermal expansion was revealed in α″ martensite of the Ti-Nb system 9,12. The successful development of novel structural and functional Ti-alloys with bespoke mechanical and shape memory behaviour depends critically on accurate descriptions of precipitation and decomposition processes. In addition, key for dimension critical components is the ability to control thermal expansion 13,14. Nowadays, the core challenge in developing new Ti-alloys lies in unravelling the complexity of phase reactions and in deriving robust thermodynamic and structural descriptions to assist the alloy design process. Empirical trial-and-error methods still prevail today, nevertheless systematic attempts are made to develop and employ predictive capabilities through ab-initio 15-19 , phase-field 20,21 and CALPHAD 22-27 methods. The...

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Insights into Phase Evolution and Mechanical Behavior of the Eutectoid Ti–6.4(wt%)Ni Alloy Modified with Fe and Cr

Pfaffinger,

Staufer,

Edtmaier

et al. 2023

Adv Eng Mater

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Titanium alloys gain increasing importance in industry due to the expansion of advanced manufacturing technologies such as additive manufacturing. Conventional titanium alloys processed by such technologies suffer from formation of large primary grains and anisotropy of mechanical properties. Therefore, novel alloys are required. Herein, the effect of ternary alloying elements Fe and Cr on the Ti–6.4(wt%)Ni eutectoid system is investigated. Both elements act as eutectoid formers. Fe and Cr show sluggish transformation behavior, whereas Ni is an active eutectoid‐forming element. Thereby, sluggish refers to slow and active to fast transformation kinetics. The focus of this work is on the combined addition of such elements studied under different heat‐treatment conditions. It is shown in the results that largely varying microstructures can be generated resulting in hardness values ranging from 239 to 556 HV0.1. Moreover, the formation of a substructure within the α phase of direct aged alloys is observed. The formation mechanism of this substructure is investigated in detail. The mechanical properties are discussed based on the microstructural characteristics. The presence of intermetallic Ti2Ni phase increases the Young's modulus, whereas the presence of ω phase results in embrittlement. The results shed light upon the complex phase formation and decomposition behavior of titanium alloys based on Ti–6.4Ni.

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Tracking the αʺ martensite decomposition during continuous heating of a Ti-6Al-6V-2Sn alloy

Cited by 55 publications

References 37 publications

Martensite Transformation and Mechanical Properties of Polycrystalline Co-Ni-Al Alloys with Gd Doping

Martensite Transformation and Mechanical Properties of Polycrystalline Co-Ni-Al Alloys with Gd Doping

Routes to control diffusive pathways and thermal expansion in Ti-alloys

Insights into Phase Evolution and Mechanical Behavior of the Eutectoid Ti–6.4(wt%)Ni Alloy Modified with Fe and Cr

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