Studies on the effect of grain refinement and thermal processing on shape memory characteristics of Cu–Al–Ni alloys
TL;DR: In this article, a grain refinement and thermomechanical processing of Ni-Ti shape memory alloys has been conducted to increase the shape memory characteristics and ductility of copper-based alloys.
Abstract: Though Ni–Ti shape memory alloys are used extensively in a variety of engineering and medical applications because of their attractive shape memory characteristics, they still suffer from certain drawbacks, such as low transformation temperatures, difficulty in production and processing and high cost of raw materials. Copper-based alloys have, therefore, come as an alternative to Ni–Ti shape memory alloys. They are easier to produce and process and are also less expensive. They are used where Ni–Ti alloys cannot be used. But Cu–Al–Ni shape memory alloys also pose problems since they are brittle and possess lower shape recovery strains and stresses. With a view to increasing the shape memory characteristics and ductility of Cu–Al–Ni shape memory alloys, they were subjected to grain refinement and thermomechanical processing. The present study establishes that grain-refining additions result in considerable reduction in the grain size of the alloys. In addition, grain refinement and alloying cause an increase in the transformation temperatures. The results are analysed in the light of the explanations/theories put forth in recent papers related to Cu–Al–Ni shape memory alloys, and an attempt has been made to compare the results.
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TL;DR: In this article, the incorporation of silver nanoparticles into Cu-based shape memory alloys is recommended to enhance their phase transformation behavior. But, this incorporation can affect their transformation temperatures, mechanical, microstructural and corrosion characteristics.
58 citations
TL;DR: In this article, the effect of Ti additions on the microstructure and mechanical properties of Cu-Al-Ni shape memory alloys (SMA) was studied by means of a differential scanning calorimeter, field emission scanning electron microscopy and X-ray diffraction (XRD).
Abstract: The effect of Ti additions on the microstructure and mechanical properties of Cu–Al–Ni shape memory alloys (SMA) was studied by means of a differential scanning calorimeter, field emission scanning electron microscopy, transmission electron microscopy, X-ray diffraction (XRD), a tensile test, a hardness test, and a shape memory effect test. The experimental results show that the Ti additions have an effective influence on the phase transformation behavior through generating a new phase into the microstructure, which is known as X-phase and/or controlling the grain size. The results of the XRD confirmed that the X-phase is a combination of two compounds, AlNi2Ti and Ti3·3Al. Nevertheless, it was found that with 0.7 mass% of Ti, the best phase transformation temperatures and mechanical properties were obtained. These improvements were due to the highest existence of the X-phase into the alloy along with a noticeable decrement of grain size. The Ti additions to the Cu–Al–Ni SMA were found to increase the ductility from 1.65 to 3.2 %, corresponding with increasing the strain recovery by the shape memory effect from 50 to 100 %; in other words, a complete recovery occurred after Ti additions.
54 citations
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...The XRD of the alloys having a monoclinic structure, which was similar to other work done earlier [30, 31]....
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10 May 2016-Materials Science and Engineering A-structural Materials Properties Microstructure and Processing
TL;DR: In this paper, the effects of grain size on the microstructure, tensile mechanical properties as well as low frequency damping behaviors of the CuAlMn SMA were studied.
Abstract: To further enhance the performances of Cu-based shape memory alloys (SMAs), grains of a CuAlMn SMA were efficiently refined by using Cu51Zr14 as the inoculant. The effects of grain size on the microstructure, tensile mechanical properties as well as low frequency damping behaviors of the CuAlMn SMA were studied. It was found that the mean grain size of the CuAlMn SMA could be reduced from around 1050 µm to around 37 µm. And it was very interesting that both the tensile mechanical property and the damping capacity at relatively low temperatures increased with the decrease of the mean grain size of the CuAlMn SMA. The associated mechanisms were discussed.
53 citations
TL;DR: In this paper, the influence of Mn addition on the structure, mechanical properties, and corrosion behavior of shape memory alloys have been studied using differential scanning calorimetry, field emission scanning electron microscopy, transmission electron microscope, x-ray diffraction, tensile test, shape memory effect test, hardness test, and electrochemical test.
Abstract: The influences of different amount (0.4, 0.7, and 1 wt.%) of Mn addition on the structure, mechanical properties, and corrosion behavior of Cu-Al-Ni shape memory alloys have been studied using differential scanning calorimetry, field emission scanning electron microscopy, transmission electron microscopy, x-ray diffraction, tensile test, shape memory effect test, hardness test, and electrochemical test. It was observed that the transformation temperatures, microstructural characteristics, and mechanical properties are highly sensitive to the composition variations. The obtained results show that the transformation temperatures and mechanical properties of Cu-Al-Ni SMAs exhibited the best results with 0.7 wt.% of Mn addition. These kinds of enhancements are mainly due to the type, amount, and morphology of the martensite phase, including the grain refinement. The result of electrochemical test showed that an increment in Mn content up to 0.7 wt.% improved the corrosion resistance of Cu-Al-Ni SMA. However, further increase of Mn content decreases the corrosion resistance of the alloy.
45 citations
TL;DR: In this article, the effects of different contents (04, 07, and 10%, mass fraction) of Mn or Ti additions on the micro structure, shape memory effect and the corrosion behaviour of Cu-Al-Ni shape memory alloys were studied by field emission scanning electron microscopy, transmission electron microscope, X-ray diffraction, differential scanning calorimetry and electrochemical and immersion tests in NaCl solution.
42 citations
References
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15 Dec 1999-Materials Science and Engineering A-structural Materials Properties Microstructure and Processing
TL;DR: In this article, the authors stress the need for further exploration of the 4P-relation: principles-properties-processing-products as well as in companies as well in universities or other research laboratories, illustrated by describing some actual applications indicating why they are successful, other applications why they failed and still others that can only be realised if some further, probably possible, material improvement can be realised.
Abstract: The diversity of (potential) applications using shape memory alloys (SMA), apart from the medical field, becomes quite large. Classic categories such as free recovery, actuators, constrained recovery, pseudo-elasticity or damping require further specifications. For example, micro-actuators, smart materials or active damping, can be all classified as actuator applications, but each of those items demands specific functional performance, dimensions and processing. Furthermore, success for applications can only be realised in so far those materials offer also a price-competitive advantage relative to other functional materials or mechanical designs. This competition requires perfect control of the material performance. It is known that especially Ni–Ti alloys can be tuned relatively easy to some specific requirements of the envisaged application: hysteresis, transformation temperatures, damping capacity. At the other side little is known on recovery stresses, wear resistance, fracture mechanics, fatigue … In this paper we would like to stress the need for further exploration of the 4P-relation: principles–properties–processing–products as well in companies as in universities or other research laboratories. This will be illustrated by describing some actual applications indicating why they are successful, other applications why they failed and still others that can only be realised if some further, probably possible, material improvement can be realised.
816 citations
TL;DR: Most of shape memory alloys are functional intermetallics as discussed by the authors, and they are now practically being used for couplings, actuators, medical guide wires etc., and are hopeful candidates for smart materials, which already exist.
777 citations
25 Jul 2004-Materials Science and Engineering A-structural Materials Properties Microstructure and Processing
TL;DR: In this paper, the shape memory effect holds so many opportunities for medical devices and a selection of current applications is reviewed in detail, considering the benefits of shape memory alloys in medical devices, and considering the factors that impinge on the associated risk analysis of using nitinol in medical applications.
Abstract: The medical market is a continuing success story for the application of shape memory alloy products. Increasing life expectancy and advances in surgical procedures mean that the medical market will remain an area of great opportunity for commercial applications. This paper will consider just why the shape memory effect holds so many opportunities for medical devices and will review a selection of current applications. Interventional radiology in particular has benefited from the unique properties of superelastic nitinol and this will be reviewed in detail. As well as considering the benefits of shape memory alloys in medical devices this paper will also consider the factors that impinge on the associated risk analysis of using nitinol in medical applications.
666 citations
TL;DR: In this article, the specific damping properties and damping functional behaviour of shape memory alloys, with special emphasis on NiTi, are discussed and illustrated by actual applications and applications under development.
315 citations
TL;DR: The microstructures, crystal structures and mechanical properties of the copper-aluminum martensites, forming from the β solid solution, have been investigated by electron microscopy, electron diffraction and hardness measurements as mentioned in this paper.
213 citations