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

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.

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

2015 ◽  
Vol 1765 ◽  
pp. 153-158 ◽  
Author(s):  
Luiz F.A. Rodrigues ◽  
Fernando A. Amorim ◽  
Francisco F.R. Pereira ◽  
Carlos J. de Araújo
Keyword(s):  
Experimental Study ◽  
Shape Memory Alloy ◽  
Shape Memory Alloys ◽  
Shape Memory ◽  
Welding Process ◽  
Functional Materials ◽  
Inert Gas ◽  
Scanning Calorimetry ◽  
Dissimilar Joints ◽  
Mechanical Cycling

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.

A Novel Fabrication Method for Nitinol Shape Memory Alloys

2010 ◽  
Vol 442 ◽  
pp. 309-315 ◽  
Author(s):  
S.A. Rizvi ◽  
T.I. Khan
Keyword(s):  
Shape Memory Alloys ◽  
Shape Memory ◽  
Compositional Analysis ◽  
Thin Foil ◽  
Optical Microscope ◽  
Scanning Calorimetry ◽  
Experimental Conditions ◽  
Cross Sectional ◽  
Joint Replacements ◽  
Laser Facility

Nitinol (NiTi) shape memory alloys are widely used in a variety of biomedical applications, such as dental implants, cervical and lumbar vertebral replacements, joint replacements and stents. In this study, commercially pure Ti and Ni foils ~100 um thick were diffusion bonded in vacuum. The experimental conditions were optimized to achieve a near equiatomic composition to produce NiTi SMA thin foil of approx. 5-8 micron thick. The cross-sectional surfaces of joint were subjected to metallographic investigation using optical microscope after grinding, polishing and etching. Scanning electron microscope equipped with EDX system was utilized to characterize the bonded layer and compositional analysis. Differential scanning calorimetry (DSC) technique was employed to determine the shape memory effect. The samples were subjected to X-ray diffraction analysis in order to establish phase structures formed during the diffusion bonding stage. An ultra fast femto-second laser facility was utilized to ensure the production of complex shapes or patterns within micron scale.

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

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.

Synthesis and Characterization of Cu-Al-Be-Mn Quaternary Shape Memory Alloys Prepared by Induction Melting Technique

2015 ◽  
Vol 813-814 ◽  
pp. 240-245 ◽  
Author(s):  
A.G. Shivasiddaramaiah ◽  
U.S. Mallikarjun ◽  
S. Prashantha
Keyword(s):  
Shape Memory Alloys ◽  
Shape Memory ◽  
Low Cost ◽  
Optical Microscope ◽  
Synthesis And Characterization ◽  
Induction Melting ◽  
Ingot Metallurgy ◽  
Scanning Calorimetry ◽  
Β Phase

Shape memory materials are stimuli-responsive materials. They are widely used in military, medical, safety, and robotics applications. Until recently, only Ni-Ti based SMA’s are commercially used due to its relatively ease of manufacturing. However, the exorbitantly high cost of Ni-Ti based SMA limits its application to niche markets such as medical stents, aerospace and defence. Recently, it is found that Cu based alloys exhibit shape memory behavior. Out of which, Cu-Al-Be-Mn is most interesting SMA in terms of less process complexity and low cost. Cu–Al–Be-Mn shape memory alloys in the range of 09–15 wt.% of aluminium and 0.1-0.4 wt.% of Beryllium and 0.1 to 0.3 wt.% of Manganese, exhibiting β-phase at high temperatures and manifesting shape memory effect upon quenching to lower temperatures, were prepared through ingot metallurgy. The alloy ingots were homogenized followed by step quenching so as to obtain a structure that is completely martensitic. They were subsequently characterized by X-ray diffractogram (XRD), Differential Scanning Calorimetry (DSC) and Optical Microscope (OM). The shape memory properties of the alloys were studied by bend test. This paper emphasizes the synthesis and characterization of the Cu-Al-Be shape memory alloys.

scholarly journals Influence of alloying elements on the thermal behavior of NiTi shape memory alloys

2021 ◽  
Vol 342 ◽  
pp. 06007
Author(s):  
Nicoleta-Monica Lohan ◽  
Çtefan-Lucian Toma ◽  
Mihai Popa ◽  
Alin Marian Cazac ◽  
Bogdan Pricop
Keyword(s):  
Shape Memory Alloys ◽  
Thermal Behavior ◽  
Shape Memory ◽  
Alloying Elements ◽  
Alloying Element ◽  
Scanning Calorimetry ◽  
Automotive Manufacturing ◽  
Niti Alloys ◽  
The Third ◽  
Niti Shape Memory Alloys

NiTi based shape memory alloys are one of the most intensely studied alloys from its class. Therefore, diverse commercial applications have been developed due to certain properties such as: shape memory effect, superelasticity and corrosion resistance. Currently, the main applications of NiTi alloys are automotive manufacturing and aerospace actuators, biomedical devices or pipe couplings. In recent years, NiTi shape memory alloys have been alloyed with a third element in order to improve the above-mentioned properties. In order to investigate the influence of the alloying elements on the thermal behavior of NiTi alloys, the addition of the third alloying element (Ta and Nb) is under investigation in the present study. The thermal behavior of the three alloys (NiTi, NiTiNb and NiTiTa) was studied by differential scanning calorimetry. Following the experiments, it was observed that the addition of the third alloying element influences the critical transformation temperatures.

Electronic and structural properties of Fe[sub 3]Pd–Pt ferromagnetic shape memory alloys

2002 ◽  
Vol 91 (10) ◽  
pp. 7818 ◽  
Author(s):  
R. A. Stern ◽  
S. D. Willoughby ◽  
A. Ramirez ◽  
J. M. MacLaren ◽  
J. Cui ◽  
...  
Keyword(s):  
Shape Memory Alloys ◽  
Shape Memory ◽  
Structural Properties ◽  
Ferromagnetic Shape Memory Alloys ◽  
Ferromagnetic Shape Memory ◽  
Electronic And Structural Properties

Thermodynamic Analysis of Thermoelastic Martensitic Transformations

2004 ◽  
Vol 449-452 ◽  
pp. 1325-0 ◽  
Author(s):  
Yinong Liu
Keyword(s):  
Shape Memory Alloys ◽  
Shape Memory ◽  
Experimental Determination ◽  
Thermodynamic Parameters ◽  
Thermodynamic Analysis ◽  
Martensitic Transformations ◽  
Thermoelastic Martensitic Transformations ◽  
The Past ◽  
Concise Overview

This paper is concerned with the application of fundamental thermodynamic theories in the analysis of thermoelastic martensitic transformations in shape memory alloys, with a particular reference to polycrystalline NiTi. The discussion is delivered in two parts. The first part presents a concise overview of the fundamental theories of thermodynamics of thermoelastic martensitic transformations established in the past 30 years. The second part focuses on the principles governing the application of the theories, interpretation of the thermodynamic parameters defined in the theories, experimental determination of the parameters, and some common misperceptions and unjustified assumptions in practice concerning these parameters.

Micro pulling down growth of very thin shape memory alloys single crystals

2017 ◽  
Vol 10 (01) ◽  
pp. 1740003 ◽  
Author(s):  
I. López-Ferreño ◽  
J. San Juan ◽  
T. Breczewski ◽  
G. A. López ◽  
M. L. Nó
Keyword(s):  
Mechanical Properties ◽  
Shape Memory Alloys ◽  
Single Crystal ◽  
Shape Memory ◽  
Single Crystals ◽  
Functional Materials ◽  
Small Scale ◽  
Cylindrical Shape ◽  
Minimum Diameter ◽  
Wide Range

Shape memory alloys (SMAs) have attracted much attention in the last decades due to their thermo-mechanical properties such as superelasticity and shape memory effect. Among the different families of SMAs, Cu–Al–Ni alloys exhibit these properties in a wide range of temperatures including the temperature range of 100–200[Formula: see text]C, where there is a technological demand of these functional materials, and exhibit excellent behavior at small scale making them more competitive for applications in Micro Electro-Mechanical Systems (MEMS). However, polycrystalline alloys of Cu-based SMAs are very brittle so that they show their best thermo-mechanical properties in single-crystal state. Nowadays, conventional Bridgman and Czochralski methods are being applied to elaborate single-crystal rods up to a minimum diameter of 1[Formula: see text]mm, but no works have been reported for smaller diameters. With the aim of synthesizing very thin single-crystals, the Micro-Pulling Down ([Formula: see text]-PD) technique has been applied, for which the capillarity and surface tension between crucible and the melt play a critical role. The [Formula: see text]-PD method has been successfully applied to elaborate several cylindrical shape thin single-crystals down to 200[Formula: see text][Formula: see text]m in diameter. Finally, the martensitic transformation, which is responsible for the shape memory properties of these alloys, has been characterized for different single-crystals. The experimental results evidence the good quality of the grown single-crystals.

Cast NiTi Shape-Memory Alloys

2004 ◽  
Vol 855 ◽  
Author(s):  
Alicia M. Ortega ◽  
Carl P. Frick ◽  
Jeffrey Tyber ◽  
Ken Gall ◽  
Hans J. Maier
Keyword(s):  
Shape Memory Alloys ◽  
Shape Memory ◽  
Grain Orientation ◽  
Mechanical Response ◽  
Complex Geometry ◽  
Low Cost ◽  
Orientation Distribution ◽  
Scanning Calorimetry ◽  
Cast Material ◽  
Niti Shape Memory Alloys

ABSTRACTThe purpose of this study is to investigate the structure and properties of polycrystalline NiTi in its cast form. Although it is commonly stated in the literature that cast NiTi has poor shape-memory behavior, this study demonstrates that with appropriate nano/micro structural design, cast NiTi possesses excellent shape-memory properties. Cast NiTi shape-memory alloys may give rise to a new palette of low-cost, complex-geometry components. Results from two different nominal compositions of cast NiTi are presented: 50.1 at.%Ni and 50.9 at.%Ni. The cast NiTi showed a spatial variance in grain size and a random grain orientation distribution throughout the cast material. However, small variances in the thermo-mechanical response of the cast material resulted. Transformation temperatures were slightly influenced by the radial location from which the material was extracted from the casting, showing a change in Differential Scanning Calorimetry peak diffuseness as well as a change in transformation sequence for the 50.9 at.%Ni material. Mildly aged 50.9 at.%Ni material was capable of full shape-memory strain recovery after being strained to 5% under compression, while the 50.1 at.%Ni demonstrated residual plastic strains of around 1.5%. The isotropic and symmetric response under tensile and compressive loading is a result of the measured random grain orientation distribution. The favorable recovery properties in the cast material are primarily attributed to the presence of nanometer scale precipitates, which inhibit dislocation motion and favor the martensitic transformation.

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