A Study on Uniaxial Tensile Deformation Behavior of Superelastic Titanium Alloy

A superelastic titanium alloy was subjected to uniaxial tensile deformation at room temperature. The microstructural evolution and deformation mechanisms of the superelastic titanium alloy were investigated by electron backscatter diffraction (EBSD) and X-ray diffraction (XRD). Multiple deformation mechanisms including stress-induced martensitic transformation (SIMT), dislocation slip, {332}<113> and {112}<111> mechanical twinning were identified with the increase in uniaxial strain. In the early stage of deformation, a SIMT from the bcc beta phase to orthorhombic martensite phase dominantly occurred. As the deformation proceeded, the phase fraction of the remained martensite which did not return to beta phase obviously increased due to dislocation slip and mechanical twinning. The kernel average misorientation (KAM) value obtained from EBSD data gradually increased with increasing the deformation, indicating that the dislocation evolution was produced by slip. This was well matched with the trend in the full width at half maximum (FWHM) value of the peak profile obtained from XRD data. In addition, the fraction of the {332}<113> twin was lower than that of the {112}<111> twin in the initial specimen. However, the {332}<113> twin rapidly increased compared to the {112}<111> twin as deformation increased. Therefore, it is confirmed that {332}<113> twinning and dislocation slip were the dominant mechanisms during plastic deformation.

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Hot Gas Pressure Forming of Ti-55 High Temperature Titanium Alloy Tubular Component

Materials ◽

10.3390/ma13204636 ◽

2020 ◽

Vol 13 (20) ◽

pp. 4636

Author(s):

Kehuan Wang ◽

Chenyu Shi ◽

Shiqiang Zhu ◽

Yongming Wang ◽

Jintao Shi ◽

...

Keyword(s):

Titanium Alloy ◽

High Temperature ◽

Tensile Deformation ◽

Electron Backscatter Diffraction ◽

Thickness Distribution ◽

Tensile Tests ◽

Gas Pressure ◽

Uniaxial Tensile ◽

Hot Gas ◽

Tubular Component

In this paper, hot gas pressure forming (HGPF) of Ti-55 high temperature titanium alloy was studied. The hot deformation behavior was studied by uniaxial tensile tests at temperatures ranging from 750 to 900 °C with strain rates ranging from 0.001 to 0.05 s−1, and the microstructure evolution during tensile tests was characterized by electron backscatter diffraction. Finite element (FE) simulation of HGPF was carried out to study the effect of axial feeding on thickness distribution. Forming tests were performed to validate this process for Ti-55 alloy. Results show that when the temperature was higher than 750 °C, the elongation was large enough for HGPF of Ti-55 alloy. Dynamic recrystallization (DRX) occurred during the tensile deformation, which could refine the microstructure. The thickness uniformity of the formed part could be improved by increasing feeding length. The maximum thinning ratio decreased from 27.7% to 11.5% with the feeding length increasing from 0 to 20 mm. A qualified Ti-55 alloy component was successfully formed at 850 °C, the microstructure was slightly refined after forming, and the average post-form yield strength and peak strength were increased by 8.7% and 6.9%, respectively. Pre-heat treatment at 950 °C before HGPF could obtain Ti-55 alloy tubular component with bimodal microstructure and further improve the post-form strength.

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How Oxygen Influences the Deformation Mechanism of the “Gum Metal” Titanium Alloy Composition

Materials Science Forum ◽

10.4028/www.scientific.net/msf.706-709.492 ◽

2012 ◽

Vol 706-709 ◽

pp. 492-497 ◽

Cited By ~ 1

Author(s):

Thierry Gloriant ◽

M. Besse ◽

Philippe Castany ◽

M. Cornen ◽

D.M. Gordin ◽

...

Keyword(s):

Titanium Alloy ◽

Deformation Mechanism ◽

Alloy Composition ◽

Tensile Tests ◽

Deformation Mechanisms ◽

Dislocation Slip ◽

Cold Crucible ◽

Levitation Melting ◽

Gum Metal ◽

Metal Titanium

In this work, Ti-23Nb-0.7Ta-2Zr (TNTZ) and “Gum Metal” Ti-23Nb-0.7Ta-2Zr-1.2O (TNTZ-O) alloys were synthesized by cold crucible levitation melting (CCLM) with the objective to investigate the influence of oxygen on the deformation mechanisms. By tensile tests and EBSD analyses, we showed that the deformation in the TNTZ-O alloy is only accommodated by dislocation slip. Thus, the addition of oxygen leads to suppress the formation of α” martensite and prevents the twinning deformation mechanism.

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Complex Structural Effects in Deformed High-Manganese Steel

Materials ◽

10.3390/ma14226935 ◽

2021 ◽

Vol 14 (22) ◽

pp. 6935

Author(s):

Joanna Kowalska ◽

Janusz Ryś ◽

Grzegorz Cempura

Keyword(s):

Mechanical Properties ◽

Phase Transformations ◽

Mechanical Twinning ◽

Carbon Steels ◽

Deformation Mechanisms ◽

Manganese Steel ◽

Dislocation Slip ◽

Chemical Compositions ◽

High Manganese ◽

Deformation Degree

The research presented in this paper is part of a larger project concerning deformation behavior, microstructure and mechanical properties of high-manganese steels with different chemical compositions and processed under various conditions. The current investigation deals with the development of microstructure and crystallographic texture of Fe-21.2Mn-2.73Al-2.99Si steel deformed in tension until fracture at ambient temperature. The deformation process of the examined steel turned out to be complex and included not only dislocation slip and twinning but also strain induced phase transformations (g ® e) and (g ® a′). The formation of e-martensite with hexagonal structure was observed within the microstructure of the steel starting from the range of lower strains. With increasing deformation degree, the a′-martensite showing a cubic structure gradually began to form. Attempts have been made to explain the circumstances or conditions for the occurrence of the deformation mechanisms mentioned above and their impact on the mechanical properties. The obtained results indicate that the strength and plastic properties of the steel substantially exceed those of plain carbon steels. Since both, mechanical twinning and the strain-induced phase transformations took place during deformation, it seems that both types of deformation mechanisms contributed to an increase in the mechanical properties of the examined manganese steel.

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Strength-Ductility Synergy in a Metastable β Titanium Alloy by Stress Induced Interfacial Twin Boundary ω Phase at Cryogenic Temperatures

Materials ◽

10.3390/ma13214732 ◽

2020 ◽

Vol 13 (21) ◽

pp. 4732

Author(s):

Yongkang Li ◽

Zhibin Liao ◽

Weidong Zhang ◽

Zhenggang Wu ◽

Canxu Zhou

Keyword(s):

Mechanical Properties ◽

Titanium Alloy ◽

Cryogenic Temperature ◽

Tensile Deformation ◽

Tensile Tests ◽

Mechanical Twinning ◽

Strong Temperature Dependence ◽

Cryogenic Temperatures ◽

Monotonic Trend ◽

Β Phase

A β titanium alloy is an excellent candidate for cryogenic applications. In this study, the deformation behavior of Ti-36Nb-2Ta-3Zr-0.35O with cold swaging was investigated at cryogenic temperatures to verify its practical application value. The microstructure after tensile tests was observed by transmission electron microscope in order to reveal the cryogenic deformation mechanism. The results show that the mechanical properties of this alloy have a strong temperature dependence: an increase in strength with a non-monotonic trend (first increase and then decrease) in elongation is found when the temperature decreases from 297 K to 77 K. At 200 K, a strength-ductility synergy is obtained and is mainly due to the occurrence of {211} <11> mechanical twinning accompanied with the ω plate located at the twin boundaries, which is the first time it is detected in titanium alloy at a cryogenic temperature. However, at 77 K, martensitic transformation (β phase to α phase) is induced by the tensile deformation, leading to the increase of strength with a massive sacrifice of elongation. These findings provide insights for understanding the deformation mechanisms and optimizing the mechanical properties of titanium alloys at a cryogenic temperature.

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Quasi-Situ Characterization of Retained Austenite Orientation in Quenching and Partitioning Steel via Uniaxial Tensile Tests

Materials ◽

10.3390/ma13204609 ◽

2020 ◽

Vol 13 (20) ◽

pp. 4609

Author(s):

Pengfei Gao ◽

Jie Liu ◽

Weijian Chen ◽

Feng Li ◽

Jingyu Pang ◽

...

Keyword(s):

Mechanical Properties ◽

Retained Austenite ◽

Mechanical Stability ◽

Volume Fraction ◽

Electron Backscatter Diffraction ◽

Early Stage ◽

Tensile Tests ◽

Uniaxial Tensile ◽

Quenching And Partitioning ◽

Austenite Grains

As a representative of the third generation of advanced high strength steel, the quenching and partitioning steel has excellent potential in automobile manufacturing. The characterization and analysis of the mechanical properties and microstructure of the quenching and partitioning steel during deformation is an effective way to explore the microstructure evolution and transformation-induced plasticity effects of complex phase steels. The relationship between the microstructure morphology and mechanical properties of a 1180 MPa-grade quenching and partitioning steel was investigated through interrupted uniaxial tensile tests plus quasi-situ electron backscatter diffraction measurements. A mixture of ferrite, martensite, and retained austenite was observed in the microstructure. It was found that the volume fraction of global retained austenite decreased linearly with the increase of displacement (0 mm–1.05 mm). The evolution of the retained austenite with typical crystal direction ranges with deformation was characterized. Results show that the orientation (111) and (311) account for the highest proportion of retained austenite grains in the undeformed sample and the mechanical stability of the (311) retained austenite grains is the best. Moreover, the retained austenite grains rotated significantly in the early stage of the specimen deformation process (around yielding), and the work hardening of the specimen was weak at this stage, simultaneously.

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