Experimental Study of Tungsten Inert Gas Pulsed Welding Applied to Ni-Ti Shape Memory Alloy Wires

ABSTRACTShape memory alloys are functional materials that can recover plastic strains between 2 and 6%. This property can be used to produce actuators for many areas as medicine, robotic, aeronautic and others. Recently, it has been observed the particular interest for shape memory alloys welding, especially to obtain Ni-Ti similar and dissimilar joints and fabricate simple or complex structures. In this sense, this work present an experimental study of tungsten inert gas pulsed welding applied to Ni-Ti shape memory alloy wires with 0.9 mm in diameter, previously heat treated at 450 °C for 20 minutes and air cooled. For that, it was carried out tensile tests at isothermal temperatures from 40 °C to 90 °C (steps of 10 °C) for welded and unwelded wires. The transformation temperatures obtained from differential scanning calorimetry were compared to verify the effect of welding process. It was also performed a stabilization process by mechanical cycling in some welded and unwelded Ni-Ti wires. The results showed a low strength and strain capacity of the weld joint at higher temperatures. Although, at lowest temperature, close to 40 °C, it was observed higher values of maximum stress and strain for welded Ni-Ti wires.

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Batch Fabrication of Shape Memory Actuated Polymer Microvalves by Transfer Bonding Techniques

Journal of Microelectronics and Electronic Packaging ◽

10.4071/1551-4897-6.4.219 ◽

2009 ◽

Vol 6 (4) ◽

pp. 219-227 ◽

Cited By ~ 5

Author(s):

T. Grund ◽

C. Megnin ◽

J. Barth ◽

M. Kohl

Keyword(s):

Shape Memory Alloy ◽

Shape Memory Alloys ◽

Shape Memory ◽

Smart Materials ◽

Life Science ◽

Functional Materials ◽

Target System ◽

Work Output ◽

Batch Fabrication ◽

High Work

Polymer based microvalves offer outstanding properties for biomedical and life science applications. They can be produced cost efficiently by batch fabrication methods. Further, by adapting the polymer material, custom-tailored properties of the valve are possible. For mechanically active microvalves, actuation with smart materials like shape memory alloys is highly attractive due to their high work output per volume and favorable scaling behavior. For the integration of such smart materials, fabrication process incompatibilities between the actuator material and the polymer target system need to be avoided. This can be achieved by novel transfer bonding technologies being optimized for batch fabrication. These technologies are demonstrated for polymer microvalves actuated by a shape memory alloy but they can also be applied to other functional materials and structures.

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Fabrication and Characterization of Cu-14Al-3.5Ni Shape Memory Alloys by Ingot Metallurgy

MRS Proceedings ◽

10.1557/proc-0888-v06-01 ◽

2005 ◽

Vol 888 ◽

Author(s):

K. Jai Ganesh ◽

Arunya Suresh

Keyword(s):

Shape Memory Alloys ◽

Shape Memory ◽

Smart Materials ◽

Optical Emission ◽

Functional Materials ◽

Cost Effective ◽

Rolled Strip ◽

Ingot Metallurgy ◽

Scanning Calorimetry ◽

Electric Resistance Furnace

ABSTRACTShape Memory Alloys (SMAs) are versatile functional materials with an I.Q of their own. This class of SMART Materials exhibit unique properties like superelasticity and shape memory effect (SME) which have made them suitable for potential applications. Although Ni-Ti SMAs have attracted attention ever since their inception in 1962, Cu based SMAs due to their ease in fabrication, cost effectiveness and high temperature properties are gaining immense popularity. This research aimed at the fabrication of Cu-14 Al-3.5 Ni (wt %) Shape Memory Alloy by a simple cost effective route and its characterization to correlate its structure and properties. The alloy of desired composition was melted in an Electric Resistance Furnace at 1473 K and cast in a metallic mould. Homogenization was carried out at 1123 K for twenty four hours followed by analysis of chemical composition by Optical Emission Spectroscopy. Transformation temperatures of the alloy were determined using Differential Scanning Calorimetry. Heat treatment operations were carried out at 1273 K for one hour followed by quenching in different media. Optical and SEM micrographs were taken at various magnifications and the formation of self accommodating martensite was observed which was further confirmed by X-Ray Diffraction technique. Further improvements in the mechanical properties of the alloy by quaternary additions of Mn and Ti have been cited. Finally, SME was observed in a rolled strip of the alloy, thus concreting the obtained results.

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Mechanical and Microstructural Characterization of Ultrasonic Welded NiTiCu Shape Memory Alloy Wires to Silver-Coated Copper Ferrules

Metals ◽

10.3390/met11121936 ◽

2021 ◽

Vol 11 (12) ◽

pp. 1936

Author(s):

Toni Sprigode ◽

Andreas Gester ◽

Guntram Wagner ◽

Thomas Mäder ◽

Björn Senf ◽

...

Keyword(s):

Shape Memory Alloy ◽

Shape Memory ◽

Spot Welding ◽

Base Material ◽

Welding Process ◽

Microstructural Characterization ◽

Tensile Tests ◽

Ultrasonic Welding ◽

Transition Temperatures ◽

Scanning Calorimetry

The aim of this study was to investigate the mechanical behavior, and the microstructure of NiTiCu shape memory alloy wires joined with silver-coated copper ferrules via ultrasonic spot welding. Therefore, the electrical resistance was measured during tensile testing, and the joints were analyzed by scanning electron microscopy. Energy-dispersive X-ray spectroscopy has determined the compounds of the developed welding zones. Furthermore, the influence of the ultrasonic welding on the transition temperatures of the NiTiCu wires was examined via differential scanning calorimetry. Tensile tests have shown that the ultimate tensile strengths of the joints reached almost 100% of that of the base material. An additional heat treatment rebuilt the typical shape memory alloy behavior after the ultrasonic welding process detwinned the martensitic wires. In addition, the B19′ structure of the welding zone and the ultrasonic spot-welding process did not affect the transition temperatures of the shape memory alloy.

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Comprehensive Testing Instrument on External Characteristics of Magnetically Controlled Shape Memory Alloy

Applied Mechanics and Materials ◽

10.4028/www.scientific.net/amm.128-129.377 ◽

2011 ◽

Vol 128-129 ◽

pp. 377-380

Author(s):

Jun Lu ◽

Cheng Wu Lin

Keyword(s):

Magnetic Field ◽

Experimental Study ◽

Shape Memory Alloy ◽

Shape Memory ◽

Deformation Rate ◽

Functional Materials ◽

Testing Device ◽

Testing Instrument ◽

Field Temperature ◽

External Characteristics

Magnetically controlled shape memory alloy (MSMA) is widely concerned because of its superior characteristics in the field of functional materials. The application of MSMA materials base on experimental study, thus a comprehensive testing device of MSMA external characteristics is developed in this paper, which can simultaneously measure deformation, pressure, temperature and magnetic field. Experimental and testing device of the instrument are analyzed and designed. The curves between MSMA deformation rate and magnetic field, temperature are obtained with the testing device. The experimental results show the device can conveniently test the external characteristics of MSMA materials.

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THERMAL PARAMETERS AND STRUCTURAL INVESTIGATIONS OF Cu-BASED SHAPE MEMORY ALLOYS IRRADIATED WITH Co-60

Euroasia Journal of Mathematics, Engineering, Natural and Medical Sciences ◽

10.38065/euroasiaorg.821 ◽

2021 ◽

Vol 8 (18) ◽

pp. 151-164

Author(s):

Şahide Nevin BALO ◽

Abdulvahap ORHAN

Keyword(s):

Shape Memory Alloys ◽

Shape Memory ◽

Thermodynamic Parameters ◽

Structural Properties ◽

Functional Materials ◽

Optical Microscope ◽

Alloying Elements ◽

Nuclear Facilities ◽

Scanning Calorimetry ◽

Structural Investigations

Gamma radiation is a type of radiation that can change the structural properties of materials. Many physical and structural properties of metals and alloys change due to defects in their crystal structures in response to irradiation. Shape memory alloys (SMAs) are functional materials and are used in mechanical devices for monitoring nuclear facilities. In this study, copper-based SMAs were used. Copper-based SMAs are very sensitive to alloying elements and small changes in element percentages. Cu-11.6Al-0.42Be, Cu-11.8Al-0.47Be, Cu-13Al-4Ni, and Cu-13.5Al-4Ni (wt%) SMA samples were irradiated with a fixed radiation dose of 50 kGy. The effect of irradiation on the thermodynamic parameters and structural properties of copper-based SMAs was investigated. The effects of irradiation on thermodynamic parameters were determined by differential scanning calorimetry (DSC). Structural examinations were made by X-ray diffraction (XRD) and optical microscope observations. Microhardness measurements were taken. The results obtained for Cu-based SMAs were evaluated both as homogeneous and irradiated samples and according to alloying elements.

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Dissimilar Laser Welding of a NiTi Shape Memory Alloy to Ti2AlNb

Metals ◽

10.3390/met11101578 ◽

2021 ◽

Vol 11 (10) ◽

pp. 1578

Author(s):

Fuguo Ge ◽

Bei Peng ◽

João Pedro Oliveira ◽

Wenchao Ke ◽

Fissha Biruke Teshome ◽

...

Keyword(s):

Shape Memory Alloy ◽

Laser Welding ◽

Shape Memory Alloys ◽

Shape Memory ◽

Niti Shape Memory Alloy ◽

Dissimilar Joints ◽

Lap Shear ◽

Ti2alnb Alloy ◽

Structural Applications ◽

Potential Applications

NiTi-based shape memory alloys and the Ti2AlNb alloy have gained increasing importance in the aerospace field. The joining of these two materials can further increment the importance and usage of these relevant engineering materials and expand their potential applications. However, when joining NiTi-based shape memory alloys to Ti-based alloys, the formation of brittle Ti-rich intermetallic compounds often occurs, significantly limiting their functionality and use. Dissimilar joints between a NiTi shape memory alloy and Ti2AlNb alloy were obtained using a 0.1 mm thick Niobium (Nb) interlayer via laser welding. By process optimization, sound joints were obtained. The microstructure evolution was assessed by means of electron microscopy, whereas the mechanical strength of the joints was evaluated using lap shear tensile testing. The best performing joints were seen to fracture at maximum loads above 1230 N, thus allowing us to consider this dissimilar pair for structural applications.

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The Influence of Hafnium Content, Cold Work, and Heat Treatment on the R-Phase Transformation of Niti Based Shape Memory Alloys

MRS Proceedings ◽

10.1557/proc-459-281 ◽

1996 ◽

Vol 459 ◽

Author(s):

Chen Zhang ◽

Paul E. Thoma ◽

Ralph H. Zee

Keyword(s):

Heat Treatment ◽

Differential Scanning Calorimetry ◽

Phase Transformation ◽

Shape Memory Alloy ◽

Shape Memory Alloys ◽

Shape Memory ◽

Cold Work ◽

Niti Shape Memory Alloy ◽

Scanning Calorimetry ◽

Complex Manner

ABSTRACTThe R-phase transformation of a Ti-rich NiTi shape memory alloy (SMA) and two ternary SMAs having the compositions Ni49Ti51-XHfx with lat% and 3at% Hf, has been investigated. The influence of cold work (CW) and heat treatment (HT) on the R-phase transformation is analyzed thermally using Differential Scanning Calorimetry (DSC). Results show that the R-phase transformation depends on the SMA composition as well as the CW and HT conditions in a complex manner. For example, the formation of R-phase upon cooling from austenite (A) is increasingly suppressed with the substitution of Hf for Ti. For the ternary SMA with 3at% Hf, the A→R and R→A transformations are observed only at relatively large amounts of CW (above approximately 40%) and at a high HT temperature (450°C). DSC results also show that for the Ti-rich NiTi and the ternary SMA containing lat% Hf, the A→R and R→A transformation temperatures (TTs) are insensitive to cold work at a HT temperature of 450°C. However, at a lower HT temperature of 350°C, the TTs are found to decrease with increasing CW. For a given CW, the A→R and R→A transformations decrease with decreasing HT temperature and the effect is greatest at high CW (>50%) conditions. An effort is made to identify the factors responsible for the observed behavior in the R-phase transformation.

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