Evolution of equiaxed alpha phase during heat treatment in a near alpha titanium alloy

Gao, Xianjun; Zeng, Weidong; Wang, Yübo; Liu, Yu; Zhang, Saifei; Wang, Qingjiang

doi:10.1016/j.jallcom.2017.07.195

Cited by 36 publications

(18 citation statements)

References 23 publications

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“…Finally, one α grain of "peanut" shape is separated into two independent equiaxial α grains, as shown in Figure 6c. Furthermore, the α/α boundary can also act as the nucleation site of β phase at temperatures around the β-transus point 22 , as is observed and marked by the small blue ellipse in Figure 4e. In summary, grains in the α phase first merge into a coarse one in a "peanut" shape, which then splits into two individual single grains below the β-transus temperature.…”

Section: Microstructural Evolution and Hardnessmentioning

confidence: 64%

“…When two of these merged α grains grow to meet each other, a "peanut" shape of α grains forms, as seen in Figure 6b. The α/α grain boundaries (red dotted lines in Figure 6b) exist among these contiguous grains with "peanut" shape, when an unstable dihedral angle is created at each of the triple point junctions 22 . To minimize surface tension, the dihedral angle will shrink and thus be stabilized by the formation of a groove.…”

Section: Microstructuresmentioning

confidence: 99%

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Microstructural Evolution and Phase Transformation of a Ti-5Nb-5Al Alloy During Annealing Treatment

Dai

Song

2019

Mat. Res.

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The microstructural evolution and phase transformation of a Ti-5Nb-5Al alloy during isothermal annealing treatment were studied in this paper. The microstructural evolution was analyzed by X-ray diffraction (XRD), scanning electron microscope (SEM) equipped with X-ray energy dispersive spectroscopy (EDS) and electron backscattering diffraction (EBSD). The first-principle calculation by density functional theory method was performed to analyze the effect of niobium diffusion on the α to β transformation. The results showed that the α phase initially grew by merging neighboring grains and then by boundary splitting with increasing the solution time below the β-transus temperature. However, the α phase disappeared absolutely above the β-transus temperature. According to the thermodynamic analysis by DFT calculations, the diffusion of niobium from β to α phase can promote the α to β transformation. After quenching in water, the acicular α' phase precipitated from β matrix with an orientation relationship of {110} bcc ||{0001} hcp and <111> bcc ||<1120> hcp , and thus increased the hardness of the alloy.

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Section: Microstructural Evolution and Hardnessmentioning

confidence: 64%

Section: Microstructuresmentioning

confidence: 99%

Microstructural Evolution and Phase Transformation of a Ti-5Nb-5Al Alloy During Annealing Treatment

Dai

Song

2019

Mat. Res.

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“…In addition, the higher temperature promotes the dislocations climbing and cross slip process, resulting in a reduction in dislocation density. Consequently, the crystal defects and distortion energy per unit volume are released and the lattice distortion partially disappear 14 . As a result, the growth of equiaxed α p is not sufficient in subsequent heat treatment.…”

Section: Methodsmentioning

confidence: 99%

Tri-modal Microstructure in Different Loading Zones Under TA15 Ti-alloy Isothermal Local Conventional Forging and Given Subsequent Heat Treatment

et al. 2019

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For TA15 Ti-alloy large-scale component, isothermal local conventional forging (ILCF) combined with subsequent heat treatment provides a feasible approach to obtain a tri-modal microstructure with attractive comprehensive performance. However the tri-modal microstructure characteristics and evolution laws in the first and second loading zones are lack of understanding. In this paper, the effects of ILCF conditions on the tri-modal microstructure in the first and second loading zones were investigated under given subsequent heat treatment and the reasonable ILCF conditions were proposed. As forging temperature increases, in both loading zones the content and aspect of equiaxed α p decrease obviously while the content and thickness of lamellar α s increase. The content and thickness of lamellar α s in the second loading zone are higher. Forged at a moderate strain rate of 0.1s-1 , the content of lamellar α s is higher, and the differences in the content and morphology of constituent phases in both loading zones are relatively small. Compared with air cooling after forging, water quenching result in more and disordered lamellar α s , and less differences in obtained tri-modal microstructure in the first and second loading zones. Under three loading passes, the uniformity of tri-modal microstructure in the first and second loading zones is better.

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“…Titanium and its alloys are used extensively in the fields of aerospace, energy, and medical industries because of their excellent properties, such as a low density, high specific strength, good corrosion resistance, and good biocompatibility [1]. Nowadays, the damage-tolerant design principle has become dominant in structural component manufacture for aerospace applications [2], which leads to a stricter requirement for mechanical properties of titanium alloys.…”

Section: Introductionmentioning

confidence: 99%

Effects of β grain-growth behaviors on lamellar structural evolution and mechanical properties of TC4–DT alloy

Dong

Cai

et al. 2020

Mater. Res. Express

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Grain-growth behaviors of TC4-DT alloy in a narrow temperature range (990°C−1050°C) were systematically investigated, and the effects of which on the lamellar structural evolution and mechanical properties were quantitatively evaluated. Microstructural observations indicated that prior β grain size increased with an increase in heat-treatment temperature and time, which was described by the modified Sellars model. The grain-growth exponent (n=2.741) and activation energy (Q=161.0 kJ mol −1 ) during β treatment were confirmed. The α colony size similar to β grain varied significantly with the heat-treatment conditions, while α plate thickness changed slightly. The Hall-Petch equation could qualitatively exhibit the relationships between the lamellar microstructure parameters (prior β grain size, α colony size, and α plate thickness) and mechanical properties (strength, ductility, and impact toughness). The fine prior β grain that contained different orientated α colonies produced more boundaries to hinder dislocation motion and crack propagation, which contributed a more circuitous crack growth path. The results indicated that the control of α colony size was critical to improve the mechanical performance of TC4-DT alloy.

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Evolution of equiaxed alpha phase during heat treatment in a near alpha titanium alloy

Cited by 36 publications

References 23 publications

Microstructural Evolution and Phase Transformation of a Ti-5Nb-5Al Alloy During Annealing Treatment

Microstructural Evolution and Phase Transformation of a Ti-5Nb-5Al Alloy During Annealing Treatment

Tri-modal Microstructure in Different Loading Zones Under TA15 Ti-alloy Isothermal Local Conventional Forging and Given Subsequent Heat Treatment

Effects of β grain-growth behaviors on lamellar structural evolution and mechanical properties of TC4–DT alloy

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