The mechanism of strength and deformation in Gum Metal

Furuta, Tadahiko; Kuramoto, Shigeru; Morris, J. W.; Nagasako, Naoyuki; Withey, Elizabeth Ann; Chrzan, D. C.

doi:10.1016/j.scriptamat.2013.01.027

Cited by 44 publications

(29 citation statements)

References 29 publications

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“…Such dislocation free shear deformation is reported to realize in bcc Ti-based alloys near the composition of stable bcc phase boundary, satisfying the following conditions: (a) the ideal shear strength is low due to quite low elastic modulus, (b) due to the presence of high density of oxide particles, dislocation glide stress is higher than the ideal shear strength, (c) stress-induced martensitic transformation is suppressed, and (d) {100} cleavage fracture is also suppressed. 5) In order to clarify the deformation mechanism of crystals, particularly the role of thermal activation in the deformation process, thermal activation analysis of plastic deformation is indispensable. However, no such trial has ever been made for Gum Metal alloys.…”

Section: Introductionmentioning

confidence: 99%

Thermally Activated Deformation of Gum Metal: A Strong Evidence for the Peierls Mechanism of Deformation

et al. 2015

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Compression deformation and stress relaxation tests have been made over a wide temperature range for Ti-based bcc alloy single crystal of Gum Metal composition to elucidate the deformation mechanism. The shear yield stress decreases rapidly with increasing temperature with decreasing slope above room temperature, tending to level off. Activation analysis showed that the activation volume becomes smaller than 10 b 3 (b: the Burgers vector) at high stress, indicating that the deformation is controlled by the Peierls mechanism at low temperature. Similar results have been obtained also for severely cold-swaged polycrystalline Gum Metal with the similar composition. These results contradict the generally accepted dislocation-free mechanism of Gum Metal.

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Section: Introductionmentioning

confidence: 99%

Thermally Activated Deformation of Gum Metal: A Strong Evidence for the Peierls Mechanism of Deformation

et al. 2015

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“…It can be noticed in figure 2 b that the maximal average temperature drop ( 0.20 K) in the specimen occurs significantly earlier than the limit of the reversible deformation ( 930 MPa) macroscopically estimated. It means that such a large limit of the reversible elastic deformation (nonlinear), highlighted as the Gum Metal "super" property [1][2][3][4], originates from other deformation mechanisms and probably cannot be described by the Lord Kelvin formula [5,6,14]. The maximal temperature growth accompanying the specimen rupture is high and equals 95.5 K. It is related to strong plastic localization of the deformation ending with rupture at the strain of around 0.18. a) b) The temperature variation plot and the thermograms (0) and (1) show that in the linear elastic regime the maximal temperature drop is observed.…”

Section: Fig 1: A) Experimental Set-up; B) Technical Drawing and C)mentioning

confidence: 99%

“…Deformation mechanisms occurring in Gum Metal are unconventional and still unclear. First they were reported to be dislocation-free and caused by changes in microstructure during elastic deformation of Gum Metal namely by: lattice rotations, giant faults and nano-disturbances [3,4]. However in further studies dislocation slips were observed in Gum Metal subjected to tension fabricated by research group [11].…”

Section: Introductionmentioning

confidence: 98%

“…Both the fabrication route and the chemical composition strongly influence the superalloy characteristics. Gum Metal is known by the following outstanding properties: ultra-low elastic modulus with very high strength, rubber-like Poisson"s ratio, superelastic nature -one digit higher in nonlinear elastic deformation (≈2.5%) when compared to other metallic materials, super-plastic nature allowing cold plastic working without hardening up to ≈90%, very low linear coefficient of thermal expansion (similar to Invar) and a constant elastic modulus in the temperature range from -200°C to +250°C (similar to Elinvar) [1][2][3][4]. The density of Gum Metal equals around 5.6 g/cc which locates it between steels and aluminium alloys.…”

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confidence: 99%

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Infrared thermography applied for experimental investigation of thermomechanical couplings in Gum Metal

Golasiński¹,

Pieczyska²,

Staszczak³

et al. 2016

Proceedings of the 2016 International Conference on Quantitative InfraRed Thermography

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Results of initial investigation of thermomechanical couplings in innovative β-Ti alloy called Gum Metal subjected to tension are presented. The experimental set-up, consisting of testing machine and infrared camera, enabled to obtain stress-strain curves with high accuracy and correlate them to estimated temperature changes of the specimen during the deformation process. Both ultra-low elastic modulus and high strength of Gum Metal were confirmed. The infrared measurements determined average and maximal temperature changes accompanying the alloy deformation process, allowed to estimate thermoelastic effect, which is related to the alloy yield point. The temperature distributions on the specimen surface served to analyze strain localization effects leading to the necking and rupture. MotivationGum Metal, a new class of β-type multifunctional titanium alloys, has attracted considerable attention in the past decade due to its outstanding mechanical properties. The underlying mechanisms of its excellent performance are still unclear. The literature reports have not covered thermographic analysis of the alloy so far. Since infrared techniques and studies of thermomechanical couplings are a great tool for better understanding of mechanical behavior and phenomena occurring in materials the present research aimed at conducting thermomechanical and thermographic investigation of Gum Metal during tension. IntroductionGum Metal is a β-type Ti-based superalloy developed in Japan and reported first in 2003 [1]. Three electronic parameters were proposed for providing β phase stability: (1) a compositional average valence number (e/a) of about 4.24; (2) a bond order (Bo value) of about 2.87; and (3) a ""d" electron-orbital energy level (Md value) of about 2.45 eV. In addition, the oxygen concentration in the alloy is restricted to a range between 0.7 and 3.0 at.% [1]. Typical compositions meeting these requirements are: Ti-12Ta-9Nb-3V-6Zr-1.5O or Ti-20Nb-3.5Ta-3.4Zr-1.2O. The fabrication route of Gum Metal includes powder sintering technique and processing by cold rolling. Both the fabrication route and the chemical composition strongly influence the superalloy characteristics. Gum Metal is known by the following outstanding properties: ultra-low elastic modulus with very high strength, rubber-like Poisson"s ratio, superelastic nature -one digit higher in nonlinear elastic deformation (≈2.5%) when compared to other metallic materials, super-plastic nature allowing cold plastic working without hardening up to ≈90%, very low linear coefficient of thermal expansion (similar to Invar) and a constant elastic modulus in the temperature range from -200°C to +250°C (similar to Elinvar) [1][2][3][4]. The density of Gum Metal equals around 5.6 g/cc which locates it between steels and aluminium alloys. The amount of oxygen in Gum Metal significantly changes its microstructure, mechanical and thermomechanical properties [7,8,11,15]. Deformation mechanisms occurring in Gum Metal are unconventional and still unclear. First they wer...

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“…However, it is now widely accepted that these alloys undergo conventional dislocation based deformation processes [7] and that the observed superelastic behaviour is a result of the reversible martensitic transformation [8,9]. Nevertheless, there are still several deformation features, such as giant faults and nanodisturbances, which are not fully understood [10,11].…”

Section: Introductionmentioning

confidence: 99%

The Behaviour of Gum Metal (Ti‐36Nb‐2Ta‐3Zr‐0.3O wt.%) During Superelastic Cycling

Jones

Vorontsov

Dye

2016

Proceedings of the 13th World Conference on Titanium

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Metastable beta titanium alloys, such as Gum Metal (Ti-36Nb-2Ta-3Zr-0.3O wt.%), have received significant attention from the biomedical field over the last decade due to their low elastic modulus. Despite initial scepticism, it is now widely accepted that these alloys undergo a stress-induced transformation when subjected to an applied load, forming an orthorhombic martensite phase within the beta matrix. The reversible nature of this transformation gives rise to superelasticity, which is of significant interest for engineering applications outside of the biomedical industry. However, little is known as to the stability of the superelastic behaviour with respect to repeated load cycling. Here the response of Gum Metal during superelastic cycling was studied in situ, using high energy synchrotron diffraction. The material was observed to accumulate permanent damage with every cycle and the critical stress required for transformation decreased. The diffraction data was used to track the evolution of the martensite phase, both as a function of applied stress and cycle number. The martensite that formed was highly textured, with two independent orientations observed on each Debye-Scherrer ring. These orientations formed at different applied stresses and had different volume fractions at the peak stress. The volume fraction at the peak stress of all martensite orientations increased with cycling, which is believed to increase the defect concentration in the material and hence influence the deformation behaviour.

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The mechanism of strength and deformation in Gum Metal

Cited by 44 publications

References 29 publications

Thermally Activated Deformation of Gum Metal: A Strong Evidence for the Peierls Mechanism of Deformation

Thermally Activated Deformation of Gum Metal: A Strong Evidence for the Peierls Mechanism of Deformation

Infrared thermography applied for experimental investigation of thermomechanical couplings in Gum Metal

The Behaviour of Gum Metal (Ti‐36Nb‐2Ta‐3Zr‐0.3O wt.%) During Superelastic Cycling

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