Deformation mechanisms and kinetics of time-dependent twinning in an α-titanium alloy

Wyatt, Z.W.; Joost, William J.; Zhu, Daoyi; Ankem, Sreeramamurthy

doi:10.1016/j.ijplas.2012.06.001

Cited by 57 publications

(18 citation statements)

References 70 publications

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“…However, twins were not detected for the current joints. In general, the formation of some types of twinning in hcp structures (α-Ti phase) is a way to accommodate plastic deformation [ 38 ]. For the Ti-6Al-4V alloy, the presence of the cubic crystalline (β-Ti phase) structure may relieve deformations through the larger amount of available slip systems of the bcc structure.…”

Section: Resultsmentioning

confidence: 99%

On the Process-Related Rivet Microstructural Evolution, Material Flow and Mechanical Properties of Ti-6Al-4V/GFRP Friction-Riveted Joints

et al. 2017

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In the current work, process-related thermo-mechanical changes in the rivet microstructure, joint local and global mechanical properties, and their correlation with the rivet plastic deformation regime were investigated for Ti-6Al-4V (rivet) and glass-fiber-reinforced polyester (GF-P) friction-riveted joints of a single polymeric base plate. Joints displaying similar quasi-static mechanical performance to conventional bolted joints were selected for detailed characterization. The mechanical performance was assessed on lap shear specimens, whereby the friction-riveted joints were connected with AA2198 gussets. Two levels of energy input were used, resulting in process temperatures varying from 460 ± 130 °C to 758 ± 56 °C and fast cooling rates (178 ± 15 °C/s, 59 ± 15 °C/s). A complex final microstructure was identified in the rivet. Whereas equiaxial α-grains with β-phase precipitated in their grain boundaries were identified in the rivet heat-affected zone, refined α′ martensite, Widmanstätten structures and β-fleck domains were present in the plastically deformed rivet volume. The transition from equiaxed to acicular structures resulted in an increase of up to 24% in microhardness in comparison to the base material. A study on the rivet material flow through microtexture of the α-Ti phase and β-fleck orientation revealed a strong effect of shear stress and forging which induced simple shear deformation. By combining advanced microstructural analysis techniques with local mechanical testing and temperature measurement, the nature of the complex rivet plastic deformational regime could be determined.

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Section: Resultsmentioning

confidence: 99%

On the Process-Related Rivet Microstructural Evolution, Material Flow and Mechanical Properties of Ti-6Al-4V/GFRP Friction-Riveted Joints

et al. 2017

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“…During creep loading, twins in -Ti grow slowly over many hundreds of hours [2,3] potentially restricted by the presence of O interstitials. Further, strain-rate sensitivity of twin width during quasi-static testing as shown in Figure 3 indicates that a time dependent mechanism is involved in twinning for some -Ti alloys [13]; despite constant total strain and total twin volume fraction across all three strain rates, twin width decreases dramatically at higher strain rates. O interstitials also impede other shear-dominated processes such as the martensitic -phase to -phase transformation in Ti [14] and Zr [15].…”

Section: Twinning and Oxygen Interstitialsmentioning

confidence: 96%

“…Figure 3. Average twin thickness measured in post-deformation samples of -Ti-1.6V (wt.%) loaded to 3% total strain at room temperature in uniaxial tension (data from [13] Hex.…”

Section: Twinning and Oxygen Interstitialsmentioning

confidence: 99%

Time Dependent Twinning and the Role of Oxygen in the Low Temperature (<0.25 Tm) Creep Behavior of Alpha Titanium Alloys

Joost

Ankem

2016

Proceedings of the 13th World Conference on Titanium

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Creep behavior in titanium alloys is critical across a broad range of applications. The microstructure and deformation mechanisms in alpha-titanium alloys contribute significantly to creep behavior and thus merit careful study in order to design and deploy improved titanium alloys. While often thought to respond almost instantaneously to loading, we will present experimental work demonstrating that twins can grow very slowly in alpha titanium alloys and that this time dependent twinning correlates with increased low temperature (<0.25 Tm) creep strain during testing. Further, through the use of density functional theory calculations in combination with other computational tools, we will present details on the interaction of oxygen interstitials with twins in titanium alloys, provide insight into the role of oxygen in creep deformation, and discuss plausible development paths to improve performance.

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“…The curve of ln  -1/T was plotted as shown in Fig.7, which has a slope that is proportional (by a factor of R) to the activation energy at that particular creep strain. The value of activation energy for deformation of α titanium when slip is the rate-limiting deformation mechanism is given in the range of 30~40 kJ/mol [17,22] , while the activation energy for twin growth is 66 kJ/mol [17,18] . The low temperature primary creep activation energy of TA2 at different strain level is always higher than the activation energy for slip but lower than that for twinning, and thus both slip and twinning are active creep deformation mechanisms for TA2 at low temperature.…”

Section: Creep Deformation Mechanismmentioning

confidence: 99%

Creep Behavior of CP-Ti TA2 at Low Temperature and Intermediate Temperature

Chang

Zhou

Peng

et al. 2017

Rare Metal Materials and Engineering

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Significant temperature and stress dependent creep behavior of commercial pure titanium TA2 was observed at low and intermediate temperature. According to the variation of creep strain with applied stress level, the relationship between threshold stress level and the corresponding creep temperature was determined. Based on short time creep tests, the constitutive equation containing steady state creep strain rate was used to extrapolate the minimum creep rate. The existence of steady state creep of commercial pure titanium TA2 was confirmed by subsequent long time creep experiments. Through the minimum creep strain rates, creep stress exponent was obtained which also indicates the accuracy of the extrapolated minimum creep strain rates. The activation energy of primary creep (approximately 60 kJ/mol) at different creep strains level was higher than the activation energy for slip controlled creep, which demonstrates the importance of twinning for the development of creep behavior of TA2 at low temperature. Moreover, according to the variation of twinning structure with deformed temperature in creep tested specimens, the temperature dependent creep behavior was interpreted and the importance of twinning for creep behavior of TA2 was confirmed.

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Deformation mechanisms and kinetics of time-dependent twinning in an α-titanium alloy

Cited by 57 publications

References 70 publications

On the Process-Related Rivet Microstructural Evolution, Material Flow and Mechanical Properties of Ti-6Al-4V/GFRP Friction-Riveted Joints

On the Process-Related Rivet Microstructural Evolution, Material Flow and Mechanical Properties of Ti-6Al-4V/GFRP Friction-Riveted Joints

Time Dependent Twinning and the Role of Oxygen in the Low Temperature (<0.25 Tm) Creep Behavior of Alpha Titanium Alloys

Creep Behavior of CP-Ti TA2 at Low Temperature and Intermediate Temperature

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