Effect of cold rolling and subsequent annealing on grain refinement of a beta titanium alloy showing stress-induced martensitic transformation

Sadeghpour, Saeed; Abbasi, S.M.; Morakabati, M.; Karjalainen, L.P.; Porter, David

doi:10.1016/j.msea.2018.06.050

Cited by 49 publications

(22 citation statements)

References 41 publications

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“…[22,23] Kinking was observed in some alloys with BCC, HCP, and FCC structures, including refractory HEAs with BCC structure. [18,22,[24][25][26][27][28][29] As kinking can be considered as a type of cooperative deformation mechanism being controlled by slip, [23] the increase in dislocation density at the first stage (Figure 3b) induced the activation of kinking. In turn, the kink band formation improved the deformability of the alloy by stress relaxation and crystal reorientation, leading to geometric softening [30] observed at the second stage.…”

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confidence: 99%

Microstructure and Mechanical Properties Evolution in HfNbTaTiZr Refractory High‐Entropy Alloy During Cold Rolling

et al. 2020

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The effect of cold rolling on the structure and mechanical properties of the HfNbTaTiZr refractory high‐entropy alloy with a single body‐centered cubic (BCC) phase structure is studied. The microhardness evolution during cold rolling to the thickness strain εth = 80% shows three distinct stages: an increase till εth ≈ 15%, a plato in the interval ≈15–40%, and again some increase at εth ≥ 40%. This behavior is found to be associated with an increase in dislocation density at the first stage, the formation of kink bands at the second stage, and the development of shear bands with fine lamellar internal substructure at the third stage. After cold rolling to 80%, the alloy demonstrates the yield strength of 1220 MPa, peak strength 1320 MPa, and elongation to fracture 3.4%. A short steady‐state flow stage is observed on the engineering stress–strain curve that can also be associated with kinking.

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confidence: 99%

Microstructure and Mechanical Properties Evolution in HfNbTaTiZr Refractory High‐Entropy Alloy During Cold Rolling

et al. 2020

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“…Typically, isothermal ω (ω iso ) phase forms uniformly in the β matrix at a lower thermal treatment temperature compared to the β-to-α transition temperature, which contributes to the homogeneous nucleation of the α precipitates with a fine-scaled size 9,12 . The formation of α' and α'' phases in the β matrix of titanium alloys was observed during rapid cooling from high temperature, as well as during stress-induced transformation in previous studies 13,14 .…”

Section: Introductionmentioning

confidence: 65%

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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“…For dislocation glide controlled plasticity, the Hall-Petch relationship suggests that the smaller the grains, the higher the strength [9]. An increase of the yield strength with decreasing grain size has been confirmed for TWIP and for TRIP Ti-alloys, but it also makes twinning more difficult which leads to a drop in work hardening rate and ductility [10], and may lead to the suppression of the stress-induced martensitic transformation in TRIP alloys [11]. Regarding the solid solution hardening effect, it starts being investigated for some compositions but so far, the increase in the yield strength remains limited [12,13] or is accompanied by a drop in the work hardening rate or the ductility [6,14].…”

Section: Introductionmentioning

confidence: 95%

Design and development of a dual-phase TRIP-TWIP alloy for enhanced mechanical properties

et al. 2020

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Triggering transformation induced plasticity (TRIP) and twinning induced plasticity (TWIP) mechanisms in metastable β titanium alloys (bcc, body centered cubic) have helped reaching unprecedented mechanical properties for Ti-alloys, including high ductility and work-hardening. Yet the yield strength of such alloys generally remains rather low. So far, mostly single-phase metastable bcc alloys have been developed. In this study, a dual phase TRIP/TWIP alloy is designed and investigated. While the β-matrix is expected to display TRIP/TWIP deformation mechanisms, the addition of a second phase, α in the present study, aims at increasing the yield strength. The composition was designed in the Ti-Cr-Sn system, based on Calphad prediction and on the semi-empirical d-electron alloy design approach. Results were compared to the published full β Ti – 8.5Cr – 1.5Sn (wt%) TRIP/TWIP alloy. The dual-phase alloy was prepared and processed to reach the desired microstructure containing about 20% α. It displays remarkable mechanical properties such as a ductility of 29%, an ultimate tensile strength of 1200 MPa and a yield strength of 760 MPa, 200MPa higher than the Reference single-phase β alloy. Analysis of the mechanical properties and deformation microstructures confirm the TRIP and TWIP effects, validating the proposed approach.

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Effect of cold rolling and subsequent annealing on grain refinement of a beta titanium alloy showing stress-induced martensitic transformation

Cited by 49 publications

References 41 publications

Microstructure and Mechanical Properties Evolution in HfNbTaTiZr Refractory High‐Entropy Alloy During Cold Rolling

Microstructure and Mechanical Properties Evolution in HfNbTaTiZr Refractory High‐Entropy Alloy During Cold Rolling

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

Design and development of a dual-phase TRIP-TWIP alloy for enhanced mechanical properties

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