Thermal treatments and transformation behavior of Cu–Al–Be shape memory alloys

López, Gabriel A.; Bréczewski, T.; Ruiz‐Larrea, I.; López‐Echarri, A.; Nó, M.L.; Juan, J. San

doi:10.1016/j.jallcom.2012.02.006

Cited by 26 publications

(15 citation statements)

References 18 publications

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“…The stabilization of martensite basically refers to a condition in which the martensite phase becomes more stable than the austenite parent phase under specific thermo‐mechanical conditions, and manifests itself through an increase of the reverse transformation temperature or a decrease of the critical stress at which the reverse transformation takes place. From early works, the origin of the stabilization was linked to quenching and thermal aging through diffusion processes, and due to the importance from both fundamental and practical points of view, particularly in Cu‐based SMA, the stabilization of martensite was the subject of many research works, most of them dealing with the stabilization during thermal treatments, although the stabilization of the martensite as a consequence of a mechanical action was also reported . Thermal stabilization was attributed in the literature to mechanisms such as reordering at the martensite interfaces, atomic ordering of the phases after quenching, and migration of quenched vacancies over the interfaces of martensite, depending of the alloy and the thermal treatment.…”

Section: Resultsmentioning

confidence: 99%

“…From early works, the origin of the stabilization was linked to quenching and thermal aging through diffusion processes, and due to the importance from both fundamental and practical points of view, particularly in Cu‐based SMA, the stabilization of martensite was the subject of many research works, most of them dealing with the stabilization during thermal treatments, although the stabilization of the martensite as a consequence of a mechanical action was also reported . Thermal stabilization was attributed in the literature to mechanisms such as reordering at the martensite interfaces, atomic ordering of the phases after quenching, and migration of quenched vacancies over the interfaces of martensite, depending of the alloy and the thermal treatment. However, although the mentioned mechanisms are the most common origin of thermal stabilization, in the present study the samples remain some years at room temperature after quenching, the nano‐compression tests were conducted also at room temperature and consequently the fast stabilization process observed during the anomalous behavior in Figures and can not be explained through diffusion processes, and kinetic stabilization or a sweeping‐up mechanism, cannot be invoked to stabilize the martensite interfaces in our case.…”

Section: Resultsmentioning

confidence: 99%

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Anomalous Behavior During Nano‐Compression Superelastic Tests on Cu‐Al‐Ni Shape Memory Alloy Micro Pillars

Gómez-Cortés

Nó

López‐Echarri

et al. 2018

Physica Status Solidi (a)

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Shape memory alloys are one of the most important families of functional materials due to superelasticity and shape memory properties. In particular Cu‐Al‐Ni alloys exhibit these properties at nanoscale, becoming potentially useful to design new smart MEMS. In this work, an anomalous behavior observed during nano‐compression superelastic tests on Cu‐Al‐Ni shape memory alloy micro pillars is reported. The study is approached by nano‐compression tests on micro and nano pillars milled by focused ion beam. The anomalous behavior on the superelastic effect is manifested by a sudden stabilization of the stress‐induced martensite, which does not undergo the reverse transformation. A transition, from superelastic to pseudoelastic‐twinning behavior, takes place during the nano‐compression tests, and is evaluated through the load‐depth curves and quantified by the mechanical damping coefficient η, which undergoes a sharp change from ultra‐high damping, η > 0.1, down to η ≈ 0.01. The stabilization of the martensite occurs under two different experimental conditions, along cycling and by applying a very high stress during superelastic tests. In both cases, a further recovery of the initial superelastic behavior is registered. The mechanisms responsible for the observed stabilization and recovery are discussed, together with the implications and further requirements for technological applications in MEMS.

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Section: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

Anomalous Behavior During Nano‐Compression Superelastic Tests on Cu‐Al‐Ni Shape Memory Alloy Micro Pillars

Gómez-Cortés

Nó

López‐Echarri

et al. 2018

Physica Status Solidi (a)

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“…[40] The chemical composition Cu-12Al-0.47Be (wt%) was chosen in order to conduct the superelastic tests at room temperature, [24] and indeed the transformation temperatures measured by differential scanning calorimetry (DSC) were M s = 247 K, M f = 194 K, A s = 233 K, A f = 263 K (martensite start and finish, and austenite start and finish, respectively). Then, the samples were annealed at 1023 K in Ar during 1800 s and quenched in boiling water at 373 K to freeze the metastable austenitic phase at room temperature and to avoid further evolution of the transformation temperatures.…”

Section: Methodsmentioning

confidence: 99%

Universal Scaling Law for the Size Effect on Superelasticity at the Nanoscale Promotes the Use of Shape‐Memory Alloys in Stretchable Devices

Fuster

Gómez-Cortés

Nó

et al. 2019

Adv Elect Materials

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stretchable materials for wearable electronics, [1,2] including a diversity of materials such as flexible semiconductors, [3] or flexible meta-materials, [4] for instance, giving place to a plethora of unforeseen applications. [5] New advances in small-scale soft robots, [6] and particularly in stretchable electronic skin, [7] are driving new fields like functional neural interfaces, [8] and implantable bioelectronics. [9] With a growing worldwide forecast market, which will exceed 200 billion dollars per year by 2027, [10] flexible and stretchable electronic and wearable technologies constitute a new paradigm in the materials science era. Most of these technologies rely on organic materials, [2,11] including shape memory polymers. [12] Nevertheless, in a recent road map in this field, [8] the key points for electrical connectors or electrode materials were well identified: exceptional electrical conductivity, high stretchability, long-term functionality, the ability to withstand high stresses, and the capability of working with low cross-sectional area. While polymers and metals currently used in flexible technologies exhibit several drawbacks (for instance low electrical conductivity in polymers and low stretching capabilities in metals), shape memory alloys (SMAs), [13] could fulfill all the above requirements. Indeed, Cu-based SMAs have an extremely high electrical conductivity, 10 7 S m −1 , [14] close to pure copper and silver (6 × 10 7 S m −1 ). [15] Thanks to the superelastic behavior, [13] network-shaped devices designed with SMAs will be dramatically stretchable and their superelastic functionality could exceed 10 7 cycles, [16] withstanding stresses above 100 MPa even at small scale. [17,18] Then, SMAs could be excellent candidates to be used as electrical connectors in flexible electronic devices, provided that the last requirement could be fulfilled, this means that the above properties would be exhibited in a very low cross-sectional area, down to 1 µm 2 section or even less.Among different families of SMAs, Ti-Ni is the most widespread SMA but shows a loss of reversibility during superelastic effect at small scale, [19] while, on the contrary, Cu-Al-Ni SMAs exhibit a good reproducible superelastic behavior at the nanoscale, [17,18] even after long-term cycling. [20,21] However, until now, Cu-Al-Ni has been the only Cu-based SMA family tested for superelasticity at nanoscale, [17,18,[20][21][22] and in order to explore new SMA families, Cu-Al-Be becomes a very attractive family because at macroscopic scale, it exhibits a longer functional (superelastic) fatigue life than the Cu-Al-Ni family. [23] Shape-memory alloys (SMAs) are the most stretchable metallic materials thanks to their superelastic behavior associated with the stress-induced martensitic transformation. This property makes SMAs of potential interest for flexible and wearable electronic technologies, provided that their properties will be retained at small scale. Nanocompression experiments on Cu-Al-Be SMA single crystals demonstrate...

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“…The main Cu-based SMAs are derived from the copper-aluminium (Cu-Al) binary system, in which the stabilization of β-phase at lower temperatures is crucial to improve their thermomechanical properties. The β-phase stabilization is achieved through heat treatments and the addition of an element such as manganese (Mn), nickel (Ni) and beryllium (Be) have been used [17]. The addition of small amounts of Be cause to a sharp decrease in the martensitic transformation temperature in Cu-Al alloys close to the eutectoid composition [18].…”

Section: Introductionmentioning

confidence: 99%

Evaluation of Nb-Ni Influence on the Mechanical Behavior in a Cu-Al-Be Shape Memory Alloy

Santiago

Alcântara

Costa

et al. 2019

CJAST

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Aims:The objective was to investigate the modifications induced by grain refiners on microstructural and mechanical behaviour of Cu-Al-Be shape memory alloy. Study Design: The experiment was conducted in a completely randomized design. Place and Duration of Study: the experiment was carried out at Methodology: The alloys were prepared by induction melting and hot rolled into strips of 1.0 mm thickness at room temperature without protective atmosphere, followed of heat treatments. Subsequently the microscope analysis, differential scanning calorimetry (DSC), and mechanical Santiago et al.; CJAST, 32(4): 1-8, 2019; Article no.CJAST.46341 2 tests were carried out. Results: The shape memory alloys produced present phase transformations corresponding to the superelastic effect (SE). Grain size reduced considerably with increases content of Nb-Ni. Additionally, the mechanical tensile testing and hardness tests verified that the addition of Nb-Ni increases the stress of the alloy. Conclusion: The manufactured of Cu-Al-Be alloys by induction melting and hot rolled without protective atmosphere is viable. The microstructure analysis shows the grain refinement in Cu-Al-Be alloys containing 1.0 wt% and 1.5wt% of Nb-Ni alloy with considerable reduction in grain size. The reduction in the grain size shows the improvement in the hardness and mechanical tensile properties. Original Research Article

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Thermal treatments and transformation behavior of Cu–Al–Be shape memory alloys

Cited by 26 publications

References 18 publications

Anomalous Behavior During Nano‐Compression Superelastic Tests on Cu‐Al‐Ni Shape Memory Alloy Micro Pillars

Anomalous Behavior During Nano‐Compression Superelastic Tests on Cu‐Al‐Ni Shape Memory Alloy Micro Pillars

Universal Scaling Law for the Size Effect on Superelasticity at the Nanoscale Promotes the Use of Shape‐Memory Alloys in Stretchable Devices

Evaluation of Nb-Ni Influence on the Mechanical Behavior in a Cu-Al-Be Shape Memory Alloy

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