Electropulsing-Induced α to β Phase Transformation of Ti–6Al–4V

2019 ◽  
Vol 141 (11) ◽  
Author(s):  
Jihui Huang ◽  
Zhutian Xu ◽  
Yujun Deng ◽  
Linfa Peng
Keyword(s):  
Phase Transformation ◽  
Transformation Process ◽  
Transformation Rate ◽  
Avrami Model ◽  
Β Phase ◽  
Specific Effects ◽  
Heating Treatment ◽  
Transus Temperature ◽  
Lower Temperature ◽  
Electropulsing Treatment

Abstract Electrically assisted forming (EAF) has been increasingly utilized as an effective auxiliary processing technology to improve the formability of hard-to-deform metals. Previous works have revealed that the phase transformation of titanium alloys subjected to electropulsing treatment (EPT) can occur at a lower temperature and in a remarkably shorter time compared with those subjected to the traditional heating treatment (THT). However, an in-depth experimental verification and further analysis is still missing so far. Therefore, to characterize the specific effects of EPT on α → β transformation process, both EPT and THT experiments were conducted on Ti–6Al–4V sheet specimens. After that, a calculation method based on the analysis of optical microscopic (OM) metallographs was developed to characterize the amount of phase transformation in EPT and THT. According to the results, it was found that the pulse current can significantly reduce the phase transus temperature and accelerate the transformation process in EPT compared with that in THT. Furthermore, the specific effects of EPT on transus temperature and phase transformation rate were investigated in detail. Based on that, the transformation kinetics of the electropulsing-induced α → β phase transformation was also analyzed using the Johnson–Mehl–Avrami model. It is revealed that the activation energies of both nucleation and growth of phase transformation are reduced by electric current. Hence, the phase transformation can start at a lower temperature and with a higher rate in EPT. The mechanism behind the effects was also discussed in detail in the present work.

scholarly journals Effect of Electropulsing Treatment on Microstructure and Mechanical Properties of a Deformed ZrTiAlV Alloy

Materials ◽  
2019 ◽  
Vol 12 (21) ◽  
pp. 3560 ◽  
Author(s):  
Zhi Nan Yang ◽  
Feng Jiang ◽  
Xu Biao Wang ◽  
Lin Qu ◽  
Yan Guo Li ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Heating Temperature ◽  
Transformation Process ◽  
Heating Process ◽  
Positive Effects ◽  
Β Phase ◽  
Treatment Processes ◽  
Conventional Heat Treatment ◽  
Electropulsing Treatment ◽  
Electron Wind

In contrast to conventional heat treatment processes, electropulsing not only heats an alloy, but also exerts some other positive effects during the heating process. In this paper, the microstructural evolution and mechanical properties of a deformed Zr40Ti5Al4V alloy after electropulsing treatment were investigated. The results showed that when the charging voltage was 2 kV, there was a slight decrease in dislocation density due to the electron wind which softened the alloy even though the highest temperature of the specimen during the treatment was only 86 °C. Increasing the charging voltage to 6 kV not only further increased the heating temperature, but accelerated the phase transformation process of α″ → β → α. The presence of the α phase strengthened the alloy but notably deteriorated its ductility. A full and refined β phase microstructure could be obtained when the charging voltage was increased to 8 kV. This simultaneously increased the strength and ductility of the alloy.

Examination of an analytical phase-transformation model

2009 ◽  
Vol 24 (5) ◽  
pp. 1761-1770 ◽  
Author(s):  
F. Liu ◽  
Y.Z. Ma ◽  
X. Hu ◽  
G.C. Yang
Keyword(s):  
Exact Solution ◽  
Phase Transformation ◽  
Analytical Model ◽  
Transformation Model ◽  
Transformation Rate ◽  
Temperature Integral ◽  
Avrami Model ◽  
Cu Alloys ◽  
Analytical Phase ◽  
Continuous Nucleation

A comparison between results of a recently published quasi-exact solution of the temperature integral used for the Avrami model of isochronal phase transformations and an analytical phase-transformation model in relation to exact solutions from numerical integration has been performed. The results for the transformed fraction from the quasi-exact solution are more precise than the corresponding results of the analytical model, whereas the results for the transformation rate from both models are sufficiently precise for the nucleation mode of site saturation or continuous nucleation. It has been further shown that an analytical solution of the transformation rate cannot be obtained using a quasi-exact solution of the temperature integral in case of mixed nucleation, and that the results of the corresponding solution with the analytical model substantially alleviate the influence of the approximated temperature integral. By this method, an analytical approach of modeling, which can substantially alleviate the deviation (of model prediction) arising from approximations to the temperature integral, has been developed. The proposed approach has been successfully applied to experimental data of the crystallization of bulk amorphous Pd-Ni-P-Cu alloys.

RE-Boronizing below Beta Transus Temperature on TC4 Titanium Alloy Surface

2013 ◽  
Vol 750-752 ◽  
pp. 651-654 ◽  
Author(s):  
Jin Sheng Li ◽  
Feng Hua Li ◽  
Li Lei ◽  
Xiao Hong Yi ◽  
Zhan Guo Fan ◽  
...  
Keyword(s):  
Rare Earth Oxide ◽  
Boride Layer ◽  
Work Piece ◽  
Hardness Profile ◽  
Beta Transus ◽  
Duplex Microstructure ◽  
Tc4 Titanium Alloy ◽  
Β Phase ◽  
Transus Temperature ◽  
Lower Temperature

Ti6Al4V (TC4) slices were boronized with rare earth oxide (RE) addition in the agent at 950°C (below β phase transus of TC4). The morphology, phases, properties and structures of TC4 matrix and boride layers were studied. The results show that the boride layer on the surface of TC4 consists of TiB2 and TiB dual compounds. The boride layer is compact, uniform and less porous compared with that obtained at 1050°C (above β phase transus of TC4), and the hardness profile and brittleness of the layers are improved to a certain extent. Lower temperature boronizing can effectively prevent the growth of coarse β phase grains. Duplex microstructure is obtained in TC4 matrix, and the work piece distortion is reduced.

Aluminum Borate Whiskers Growing by Compensation of TiB2

2006 ◽  
Vol 313 ◽  
pp. 115-120
Author(s):  
Dong Ming Zhang ◽  
You Jun Li ◽  
Lian Meng Zhang ◽  
Jing Kun Guo
Keyword(s):  
Phase Transformation ◽  
Transformation Process ◽  
Aluminum Borate ◽  
Phase Transformation Process ◽  
Higher Temperature ◽  
Lower Temperature

Aluminum borate whiskers with TiB2 as borate source were prepared in this paper. The phase transformation process was analyzed by XRD and TG-DSC. The results indicate that TiB2 was decomposed into TiO2 and B2O3 in the calcining process in the active [O] atmosphere. 2Al2O3.B2O3 was formed in the lower temperature with reaction of Al2O3 and B2O3, while 9Al2O3.2B2O3 whiskers were grown by compensation of 2Al2O3.B2O3 at higher temperature (above 1050oC)

Phase Transformation In Ti-6al-4v Alloys

1972 ◽  
Vol 30 ◽  
pp. 584-585
Author(s):  
Shiro Fujishiro
Keyword(s):  
Phase Transformation ◽  
Grain Boundary ◽  
Cryogenic Temperature ◽  
Β Phase ◽  
Heat Treated ◽  
Mixed Microstructure ◽  
Ductile Behavior

The Ti-6 wt.% Al-4 wt.% V commercial alloys have exhibited an improved formability at cryogenic temperature when the alloys were heat-treated prior to the tests. The author was interested in further investigating this unusual ductile behavior which may be associated with the strain-induced transformation or twinning of the a phase, enhanced at lower temperatures. The starting materials, supplied by RMI Co., Niles, Ohio were rolled mill products in the form of 40 mil sheets. The microstructure of the as-received materials contained mainly ellipsoidal α grains measuring between 1 and 5μ. The β phase formed an undefined grain boundary around the a grains. The specimens were homogenized at 1050°C for one hour, followed by aging at 500°C for two hours, and then quenched in water to produce the α/β mixed microstructure.

Microstructural and Microchemical Characterization of Nickel Sulfide Inclusions in Plate Glass

1991 ◽  
Vol 49 ◽  
pp. 962-963
Author(s):  
J. Cooper ◽  
O. Popoola ◽  
W. M. Kriven
Keyword(s):  
Thermal Expansion ◽  
Phase Transformation ◽  
Glass Matrix ◽  
Nickel Sulfide ◽  
Plate Glass ◽  
Thermal Expansion Mismatch ◽  
Volume Increase ◽  
Β Phase ◽  
Microchemical Characterization

Nickel sulfide inclusions have been implicated in the spontaneous fracture of large windows of tempered plate glass. Two alternative explanations for the fracture-initiating behaviour of these inclusions have been proposed: (1) the volume increase which accompanies the α to β phase transformation in stoichiometric NiS, and (2) the thermal expansion mismatch between the nickel sulfide phases and the glass matrix. The microstructure and microchemistry of the small inclusions (80 to 250 μm spheres), needed to determine the cause of fracture, have not been well characterized hitherto. The aim of this communication is to report a detailed TEM and EDS study of the inclusions.

scholarly journals Dynamic Softening Mechanisms and Microstructure Evolution of TB18 Titanium Alloy during Uniaxial Hot Deformation

Metals ◽  
2021 ◽  
Vol 11 (5) ◽  
pp. 789
Author(s):  
Qiang Fu ◽  
Wuhua Yuan ◽  
Wei Xiang
Keyword(s):  
Titanium Alloy ◽  
Dynamic Recovery ◽  
True Strain ◽  
Hot Workability ◽  
Compression Tests ◽  
Phase Zone ◽  
Β Phase ◽  
Stability And Instability ◽  
Dynamic Softening ◽  
Transus Temperature

In this study, isothermal compression tests of TB18 titanium alloy were conducted using a Gleeble 3800 thermomechanical simulator for temperatures ranging from 650 to 880 °C and strain rates ranging from 0.001 to 10 s−1, with a constant height reduction of 60%, to investigate the dynamic softening mechanisms and hot workability of TB18 alloy. The results showed that the flow stress significantly decreased with an increasing deformation temperature and decreasing strain rate, which was affected by the competition between work hardening and dynamic softening. The hyperbolic sine Arrhenius-type constitutive equation was established, and the deformation activation energy was calculated to be 303.91 kJ·mol−1 in the (α + β) phase zone and 212.813 kJ·mol−1 in the β phase zone. The processing map constructed at a true strain of 0.9 exhibited stability and instability regions under the tested deformation conditions. The microstructure characteristics demonstrated that in the stability region, the dominant restoration and flow-softening mechanisms were the dynamic recovery of β phase and dynamic globularization of α grains below transus temperature, as well as the dynamic recovery and continuous dynamic recrystallization of β grains above transus temperature. In the instability region, the dynamic softening mechanism was flow localization in the form of a shear band and a deformation band caused by adiabatic heating.

γ→β phase transformation in Ti-42.9Al-4.6Nb–2Cr

2021 ◽  
Vol 133 ◽  
pp. 107169
Author(s):  
R.R. Xu ◽  
M.Q. Li
Keyword(s):  
Phase Transformation ◽  
Β Phase

scholarly journals The effect of air temperature on hospital admission of adults with community acquired pneumonia in Baotou, China

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Wenfang Guo ◽  
Letai Yi ◽  
Peng Wang ◽  
Baojun Wang ◽  
Minhui Li
Keyword(s):  
Hospital Admission ◽  
Air Temperature ◽  
Meteorological Data ◽  
Community Acquired Pneumonia ◽  
Adult Patients ◽  
Distributed Lag ◽  
Specific Effects ◽  
Lower Temperature Range ◽  
Lower Temperature ◽  
Inner Mongolia Autonomous Region

AbstractThe relationship between air temperature and the hospital admission of adult patients with community-acquired pneumonia (CAP) was analyzed. The hospitalization data pertaining to adult CAP patients (age ≥ 18 years) in two tertiary comprehensive hospitals in Baotou, Inner Mongolia Autonomous Region, China from 2014 to 2018 and meteorological data there in the corresponding period were collected. The exposure–response relationship between the daily average temperature and the hospital admission of adult CAP patients was quantified by using a distributed lag non-linear model. A total of 4466 cases of adult patients with CAP were admitted. After eliminating some confounding factors such as relative humidity, wind speed, air pressure, long-term trend, and seasonal trend, a lower temperature was found to be associated with a higher risk of adult CAP. Compared to 21 °C, lower temperature range of 4 to –12 °C was associated with a greater number of CAP hospitalizations among those aged ≥ 65 years, and the highest relative risk (RR) was 2.80 (95% CI 1.15–6.80) at a temperature of − 10 °C. For those < 65 years, lower temperature was not related to CAP hospitalizations. Cumulative lag RRs of low temperature with CAP hospitalizations indicate that the risk associated with colder temperatures appeared at a lag of 0–7 days. For those ≥ 65 years, the cumulative RR of CAP hospitalizations over lagging days 0–5 was 1.89 (95% CI 1.01–3. 56). In brief, the lower temperature had age-specific effects on CAP hospitalizations in Baotou, China, especially among those aged ≥ 65 years.

Influence of material parameters on 2D-martensitic transformation based on the phase-field finite-element method

2019 ◽  
Vol 116 (6) ◽  
pp. 614
Author(s):  
Li Chang ◽  
Gao Jingxiang ◽  
Zhang Dacheng ◽  
Chen Zhengwei ◽  
Han Xing
Keyword(s):  
Finite Element Method ◽  
Finite Element ◽  
Phase Transformation ◽  
Martensitic Transformation ◽  
Phase Field ◽  
Martensite Transformation ◽  
Transformation Process ◽  
Martensite Phase ◽  
Phase Field Method ◽  
Element Method

Obtaining an accurate microscopic representation of the martensitic transformation process is key to realizing the best performance of materials and is of great significance in the field of material design. Due to the martensite phase transformation is rapidly, the current experimental is hard to capture all the information in the Martensite phase transformation process. Combining the phase-field method with the finite-element method, a model of martensitic transformation from a metastable state to a steady state is established. The law of a single martensite nucleus during martensitic transformation is accurately described. By changing the key materials that affect martensite transformation and the phase-field parameters, the effects of the parameters on the single martensitic nucleation process are obtained. This study provides an important theoretical basis for effectively revealing the essence of martensite transformation and can determine effective ways to influence martensite transformation, obtain the optimal parameters and improve the mechanical properties of such materials.

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