Martensitic transformation from β to α′ and α″ phases in Ti–V alloys: A first-principles study

Mei, Wei; Sun, Junqiang

doi:10.1557/jmr.2017.276

Cited by 34 publications

(9 citation statements)

References 38 publications

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“…Alloy composition plays a central role in determining the transformations' nature and sequence 29,30 . Here we restrict our discussion to salient features of α″-martensitic alloys of intermediate Nb content (9)(10)(11)(12)(13)(14)(15)(16)(17)(18)(19) at.%) in the context of the foregoing analysis of the thermodynamic landscape. The Gibbs free energy relationships (Fig.…”

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confidence: 99%

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

Bönisch

Stoica

Calin

2020

Sci Rep

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“…A 30h se observa que la máxima cantidad de fase TiTaSn-β, fue de un 79,80% en peso, predominando la transformación de fases αβ. Posteriormente, a las 50h se identificó un incremento de la fase TiTaSn-α y TiTaSn-γ, lo que muestra que ocurren las siguientes transformaciones reportadas en literatura, βα [44] y βγ [45]. Finalmente, a 100h, se observó un incremento en TiTaSn-β y TiTaSn-γ, indicando que ocurren las transformaciones αβ y αγ, inducida por las altas deformaciones causadas por el aleado mecánico [46,47].…”

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“…Esa información es relevante para analizar , la posibilidad de la recristalización mecánica, y saber qué fase se está formando [41][42][43]. En todos los refinamientos se obtuvieron valores de bondad de ajuste (χ 2 ) y R wp inferiores a 2 y 10%, respectivamente, lo que muestra buena calidad del refinamiento [44,45]. En la Figura 4 se muestra un ejemplo del refinamiento de la muestra Ti-13Ta-3Sn (%at.)…”

Section: Resultsunclassified

Estudio de perfiles de difracción de rayos X de una aleación Ti-13Ta-3Sn obtenida por aleado mecánico

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RESUMEN Las aleaciones Ti-β se han vuelto altamente demandadas en la industria, por sus buenas características físicas y químicas. En el presente trabajo, se sintetizó una aleación Ti-13Ta-3Sn (%at) por aleado mecánico con tiempos entre 2 y 100h. Las aleaciones se caracterizaron por difracción de rayos X (DRX) y los patrones se analizaron por el método Rietveld con el software MAUD. Se caracterizaron los cambios microestructurales y la evolución de las fases Ti-α y Ti-β. Se identificó la presencia una nueva fase metaestable fcc y la síntesis de una aleación con un 79,80% en peso de fase Ti-β, ambas con tamaño de cristalita nanométrico.

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“…and atomic shuffle (y) = 0 for the β phase, b/a = 3 √ and y = 1/6 for α ′ phase, and b/a is from 2 √ to 3 √ and y is from 0 to 1/6 for α ′′ phase. 51,54 The nature of alloying elements and concentration of alloying elements determines the formation of α ′ and α ′′ martensitic phases for a given alloy. In binary Ti-Nb alloy, the Nb concentration of more than 11-13 wt% changes the phase transformation preference α ′ martensitic phase to α ′′ martensite phase.…”

Section: Martensitic Phasesmentioning

confidence: 99%

“…Figure 11. Schematic representation of crystal structures of β, α ′′ and α ′ phases and their lattice correspondence with basal planes as (011) β plane for β, (0001) α ′ plane for α ′ and (001) α ′ ′ for α ′′ phases 51. …”

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A review on various phases and alloy design methods of β-Ti alloys for biomedical applications

Kanapaakala

Sathesh

2023

Proceedings of the Institution of Mechanical Engineers, Part L:

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The development of biocompatible and biomechanical compatible metallic biomaterials is essential to fulfilling the needs of humanity, such as enhancing the lifespan and quality of human life and relieving pain. Biocompatibility resulting from non-toxic alloying elements and biomechanical compatibility resulting from low elastic modulus are crucial factors influencing the performance and service life of a biomedical implant. β-Ti alloys are the potential choice for biomedical load-bearing applications owing to their low elastic modulus and non-toxic alloying elements. Although the elastic modulus of β-Ti alloys is lesser than that of other metallic biomaterials, it is still greater than that of bone. So, there is a great demand for the synthesis of β-Ti alloys with low elastic modulus. Various phases significantly affect the elastic modulus of β-Ti alloys. Developing low elastic modulus β-Ti alloys through trial-and-error testing leads to more time-consuming and economically not feasible. So, this review article discusses various phases and alloy design methods for synthesising β-Ti alloys with low elastic modulus.

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Martensitic transformation from β to α′ and α″ phases in Ti–V alloys: A first-principles study

Abstract: Abstract

Cited by 34 publications

References 38 publications

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

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

Estudio de perfiles de difracción de rayos X de una aleación Ti-13Ta-3Sn obtenida por aleado mecánico

A review on various phases and alloy design methods of β-Ti alloys for biomedical applications

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