Phase Transformations and Characterization of α + β Titanium Alloys

Motyka, Maciej; Kubiak, Krzysztof; Sieniawski, Jan; Ziaja, W.

doi:10.1016/b978-0-08-096532-1.00202-8

Cited by 47 publications

(40 citation statements)

References 15 publications

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“…The α phase comprised a hexagonal closepacked (HCP) crystal structure, while the β phase was body-centered cubic (bcc). 29 The microstructure of Ti-6Al-4V alloy, which mainly depends on the heat treatment history, has strong influence on both the mechanical properties 30 and the corrosion resistance [31][32] of the alloy. The ternary phase diagram of the Ti-Al-V system suggests that at 1,050°C, β is the stable phase.…”

Section: Microstructurementioning

confidence: 99%

The influence of cold plastic deformation on passivity of Ti-6Al-4V alloy studied by electrochemical and local probing techniques

2015

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The influence of cold plastic deformation on passivity of Ti-6Al-4V alloy (UNS R56400) was investigated by means of potentiodynamic polarization, Mott-Schottky analysis, atomic force microscopy, and scanning Kelvin probe force microscopy. The results showed that the cold working increased the passive current density. Mott-Schottky analysis revealed the n-type semiconducting behavior of the passive film. The donor density of the passive film was declined by increasing the film formation potential. On the other hand, work hardening increased the density of defects within the passive film, regardless of the applied potential. The Volta potential maps showed that α phase possesses lower surface potential compared to the β, i.e., 38.6 mV. The plastic deformation decreased the surface potential of both phases; however, the relative nobility of the constituent phases had been slightly affected by cold working, i.e., 5 mV. The topographic results after immersion of the alloy in an aggressive acidic environment revealed that the Volta potential difference between α and β was sufficient to make α more vulnerable to corrosion attacks.

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Section: Microstructurementioning

confidence: 99%

The influence of cold plastic deformation on passivity of Ti-6Al-4V alloy studied by electrochemical and local probing techniques

2015

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“…The high heating rate increases the driving force for α-to-β transformation, which promotes the transformation of equiaxed α and the coarse lamellar α. The β-to-α phase transformation is accompanied by a volume contraction of 0.15-0.3% [19]. In two-phase titanium alloy, the overall expansion was related to the expansions of the constituent phases and the relative volume fractions.…”

Section: Analysis Of Differential Scanning Calorimetry and Dilatometrymentioning

confidence: 99%

“…During continuous heating, the length change of the specimens was influenced in the following aspects: the dilatation by lattice change, the thermal expansion of the lattice and additional expansion of the β lattice due to the impoverishment of β stabilizers [20]. Because the sample length variation during phase transformation was not apparent The β-to-α phase transformation is accompanied by a volume contraction of 0.15-0.3% [19]. In two-phase titanium alloy, the overall expansion was related to the expansions of the constituent phases and the relative volume fractions.…”

Section: Analysis Of Differential Scanning Calorimetry and Dilatometrymentioning

confidence: 99%

The Effect of Initial Structure on Phase Transformation in Continuous Heating of a TA15 Titanium Alloy

Fan

Zhao

et al. 2017

Metals

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Abstract:The effect of initial structure on phase evolution in continuous heating of a near-α TA15 titanium alloy (Ti-6Al-2Zr-1Mo-1V) was experimentally investigated. To this end; three microstructures were obtained by multiple heat treatment: I-bimodal structure with 50% equaixed α, II-bimodal structure with 15% equiaxed α, III-trimodal structure with 18% equiaxed α and 25% lamellar α. Differential scanning calorimetry (DSC), dilatometry and quantitative metallography were carried out on specimens with the three initial structures at heating rates from 5 to 40 • C/min. The transformation kinetics was modeled with the Johnson-Mehl-Avrami (JMA) approach under non-isothermal condition. It was found that there exists a four-stage transformation for microstructures I and III. The secondary and third stages overlap for microstructure II. The four stages of phase transformation overlap with increasing heating rate. In the presence of α laths, the phase transformation kinetics is affected by the composition difference between lamellar α and primary equiaxed α. Phase transformation is controlled by the growth of existing large β phase.

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“…The microstructure and mechanical behavior of TC4 alloy are very sensitive to the history of the thermomechanical deformation and thermochemical treatment [6][7][8][9]. Ahmed [10] found that the transformation mechanism of TC4 alloy is complete martensite, massive transformation and diffusion transformation with the cooling rate decreasing from 525 • C/s to 1.5 • C/s.…”

Section: Introductionmentioning

confidence: 99%

Study on Transformation Mechanism and Kinetics of α’ Martensite in TC4 Alloy Isothermal Aging Process

et al. 2020

Crystals

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The law of microstructure evolution and transformation mechanism of the α′ martensite decomposition during 400–600 °C were studied by the isothermal dilatometry. The transformation process of α′ martensite was quantitatively characterized based on Johnson–Mehl–Avrami (JMA) model, and the microstructure evolution under different aging processes was observed and compared on Scanning Electron Microscopy (SEM) and Transmission Electron Microscopy (TEM). The results showed that α′ → α + β is the elemental diffusion transformation, the position and shape of the precipitate gradually change with the holding time and temperature. The decomposition rate of α′ martensite was positively correlated with the aging temperature. The whole transformation process was divided into two stages based on the value of the Avrami exponent n, and the corresponding average values of the transformation activation energies Q are 46.1 kJ/mol and 116.8 kJ/mol, respectively. The calculated model had good agreement with the experimental data, and the transformation curve of α′ martensite with time and temperature during the isothermal aging at 400–600 °C was drawn.

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Phase Transformations and Characterization of α + β Titanium Alloys

Cited by 47 publications

References 15 publications

The influence of cold plastic deformation on passivity of Ti-6Al-4V alloy studied by electrochemical and local probing techniques

The influence of cold plastic deformation on passivity of Ti-6Al-4V alloy studied by electrochemical and local probing techniques

The Effect of Initial Structure on Phase Transformation in Continuous Heating of a TA15 Titanium Alloy

Study on Transformation Mechanism and Kinetics of α’ Martensite in TC4 Alloy Isothermal Aging Process

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