A study of epitaxial growth behaviors of equiaxed alpha phase at different cooling rates in near alpha titanium alloy

Gao, Xianjun; Zeng, Weidong; Zhang, Saifei; Wang, Qingjiang

doi:10.1016/j.actamat.2016.10.012

Cited by 88 publications

(15 citation statements)

References 18 publications

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“…Classical quasi-analytical models for α precipitation have been developed by Semiatin and co-workers [8,9]. They used the Ivantsov solution [10] for parabolic growth in an infinite medium, which was developed for the cases of 2D paraboloids by Horvay and Cahn [11], taking the spherical solution to examine globular precipitate growth during the globularisation heat treatment step in Ti-6Al-4V [12,13].…”

Section: Introductionmentioning

confidence: 99%

The Kinetics of Primary Alpha Plate Growth in Titanium Alloys

Ackerman

Knowles

Gardner

et al. 2019

Metall Mater Trans A

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The kinetics of primary α-Ti colony/Widmanstätten plate growth from the β are examined, comparing model to experiment. The plate growth velocity depends sensitively both on the diffusivity D(T ) of the rate-limiting species and on the supersaturation around the growing plate. These result in a maxima in growth velocity around 40 K below the transus, once sufficient supersaturation is available to drive plate growth. In Ti-6246, the plate growth velocity was found to be around 0.32 µm min −1 at 850 • C, which was in good agreement with the model prediction of 0.36 µm min −1 . The solute field around the growing plates, and the plate thickness, was found to be quite variable, due to the intergrowth of plates and soft impingement. This solute field was found to extend to up to 30 nm, and the interface concentration in the β was found to be around 6.4 at.% Mo. It was found that increasing O content will have minimal effect on the plate lengths expected during continuous cooling; in contrast, Mo approximately doubles the plate lengths obtained for every 2 wt.% Mo reduction. Alloys using V as the β stabiliser instead of Mo are expected to have much faster plate growth kinetics at nominally equivalent V contents. These findings will provide a useful tool for the integrated design of alloys and process routes to achieve tailored microstructures.

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Section: Introductionmentioning

confidence: 99%

The Kinetics of Primary Alpha Plate Growth in Titanium Alloys

Ackerman

Knowles

Gardner

et al. 2019

Metall Mater Trans A

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“…Semia n et al [4] observed that α p exhibits epitaxial growth for Ti-6Al-4V, and that it is controlled by the diffusion of vanadium. The presence of a rim-α phase in a near α Ti60 [3] surrounding the α p during cooling with the same crystallographic orienta on, evidences the epitaxial growth of α p phase. The nuclea on and growth of allotriomorphic α (α GB ) is dependent on the cooling rate and follows a platelet-like forma on [2], [4].…”

Section: Introductionmentioning

confidence: 82%

“…Thus, the resul ng microstructure consists almost en rely of large equiaxed αp with small amounts of retained β phase [2]. The amount of α p decreases for increasing cooling rates and other morphologies of α phase are formed [3]. Semia n et al [4] observed that α p exhibits epitaxial growth for Ti-6Al-4V, and that it is controlled by the diffusion of vanadium.…”

Section: Introductionmentioning

confidence: 99%

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Phase transformation sequence of Ti-6Al-4V as a function of the cooling rate

Buzolin

Weiß²,

Krumphals

et al. 2020

MATEC Web Conf.

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The growth kinetics of allotriomorphic α along the prior β grain boundaries and of globular primary α in Ti-6Al-4V during continuous cooling is described. A physical model is developed based on classical nucleation and growth of platelets for the allotriomorphic α. The growth of the primary α is modelled based on the growth of spherical particle immerged on a supersaturated β-matrix. Continuous cooling tests at two different holding temperatures in the α+β field, 930°C and 960°C, and five different cooling rates, 10, 30, 40, 100 and 300°C/min, are conducted to validate the proposed models and elucidate the growth sequence of those α morphologies. Additionally, interrupted tests at different temperatures are conducted to determine the progress of growth of primary α and formation allotriomorphic α during cooling. The size of primary α increases while its size distribution broadens with a decrease in cooling rate. Area fractions of primary α decrease with increasing cooling rate and increasing holding temperature. Moreover, the lower the cooling rate, the thicker the plates of allotriomorphic α. At the beginning of the cooling, growth of primary α, as well as formation of allotriomorphic α plates is observed. The experimental and modelled results show good agreement.

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“…In fact, the Al content in each α p particle is inhomogeneous. The interior of α p particle has a higher Al content than rim part [20]. The higher Al content makes α p more stable.…”

Section: Microstructural Investigationmentioning

confidence: 99%

Dependence of Macro- and Micro-Properties on α Plates in Ti-6Al-2Zr-1Mo-1V Alloy with Tri-Modal Microstructure

Shen

Wei

et al. 2018

Metals

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Tri-modal microstructure is often the target microstructure of titanium alloy components. In this study, the parameters, such as volume fraction, size of primary equiaxed α (α p ), secondary lamellar α (α s ) and thin α plates (α t ) in tri-modal microstructure of Ti-6Al-2Zr-1Mo-1V alloy are adjusted by double heat treatment procedures. The properties of these constituent phases and their effect on the macro-properties are then investigated. The results show that the hardness of primary α (α p ) varies slightly with heat treatment routes. The hardness of α plates region including α s and α t increases with increasing α t volume fraction and not with decreasing thickness of α s and α t . Using volume average of the thickness of α s and α t as effective thickness (t eff ), the hardness of α plates region and t eff follow the Hall-Petch relationship. Meanwhile, as α t volume fraction increases, colony structure of α s is gradually destroyed, which makes each α s have large deformation degree by multiple directions slip. When volume fraction ratio of α p , α s and α t is about 1:1:1, α p and α s can undergo relatively large deformation and α t can contribute relatively large strength to the alloy and therefore the alloy has both good strength and ductility.

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A study of epitaxial growth behaviors of equiaxed alpha phase at different cooling rates in near alpha titanium alloy

Cited by 88 publications

References 18 publications

The Kinetics of Primary Alpha Plate Growth in Titanium Alloys

The Kinetics of Primary Alpha Plate Growth in Titanium Alloys

Phase transformation sequence of Ti-6Al-4V as a function of the cooling rate

Dependence of Macro- and Micro-Properties on α Plates in Ti-6Al-2Zr-1Mo-1V Alloy with Tri-Modal Microstructure

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