scholarly journals Acoustic Emission Characteristics and Change the Transformation Entropy after Stress-Induced Martensite Stabilization in Shape Memory Ni53Mn25Ga22 Single Crystal

Materials ◽  
2020 ◽  
Vol 13 (9) ◽  
pp. 2174 ◽  
Author(s):  
László Zoltán Tóth ◽  
Lajos Daróczi ◽  
Elena Panchenko ◽  
Yuri Chumlyakov ◽  
Dezső László Beke
Keyword(s):  
Phase Transition ◽  
Acoustic Emission ◽  
Shape Memory ◽  
Emission Characteristics ◽  
Cumulative Number ◽  
Aged Sample ◽  
Scanning Calorimetry ◽  
Energy Distributions ◽  
Heating And Cooling ◽  
Martensite Stabilization

Measurements have been carried out to compare stress-induced martensite stabilization aged (SIM-aged) and as grown shape memory Ni53Mn25Ga22 single crystals with the means of simultaneous differential scanning calorimetry (DSC) and acoustic emission (AE). Contrary to expectations, the position of the hysteresis practically did not change, whilst the width of the hysteresis increased, and the forward and reverse transitions became sharper in the SIM-aged sample. The energy distributions of acoustic hits showed regular power law behaviour and the energy exponents were slightly different for heating and cooling; this asymmetry had different signs for the SIM-aged and as grown samples. During heating, in accordance with the sharper transitions observed in the DSC runs, two well-marked jumps could be seen on the plot of cumulative number of the acoustic emission events. Therefore, these were attributed to high sudden jumps in the phase transition during heating observed in the DSC. The effect of the SIM-aging on the transformation entropy was also investigated and it was found that it was about 36% less in the case of the SIM-aged sample.

scholarly journals Effect of Stress-Induced Martensite Stabilization on Acoustic Emission Characteristics and the Entropy of Martensitic Transformation in Shape Memory Ni51Fe18Ga27Co4 Single Crystal

Metals ◽  
2020 ◽  
Vol 10 (4) ◽  
pp. 534 ◽  
Author(s):  
Nora Mohareb Samy ◽  
Lajos Daróczi ◽  
László Zoltán Tóth ◽  
Elena Panchenko ◽  
Yury Chumlyakov ◽  
...  
Keyword(s):  
Phase Transition ◽  
Acoustic Emission ◽  
Shape Memory ◽  
High Energy ◽  
Emission Characteristics ◽  
Long Range Order ◽  
Aged Sample ◽  
Scanning Calorimetry ◽  
Energy Distributions ◽  
Martensite Stabilization

Simultaneous differential scanning calorimetry, DSC, and acoustic emission, AE, measurements were carried out for single crystals of quenched and stress-induced martensite stabilized (SIM-aged) shape memory Ni51Fe18Ga27Co4 alloy. The transformation temperatures were shifted to higher values, the forward (from austenite to martensite) and reverse transitions became sharper and the width of the hysteresis increased in the SIM-aged sample. The energy distributions of acoustic hits showed similar behaviour to those of the quenched sample and the energy exponents, characterizing the power law behaviour, were also similar. For SIM-aged alloys at heating, in accordance with the sharper (burst-like) transition observed in the DSC run, few high-energy solitary hits were observed, and these hits did not fit to the energy distribution function fitted for smaller energies. Thus, these high-energy events were attributed to high sudden jumps in the phase transition during heating. The effect of long-range order (by applying a heat treatment at 573 K for 6 h to transform the B2 austenite to ordered L21 structure) and the SIM-aging on the transformation entropy was also investigated by DSC. It was found that the entropy was about 36% smaller after SIM-aging of the quenched sample and it was practically unchanged after austenite stabilization.

Aging Effects of Cu-Zn-Al Shape Memory Alloys Studied by the Alchemi Measurements

1991 ◽  
Vol 246 ◽  
Author(s):  
K. Shimizu ◽  
Y. Nakata ◽  
O. Yamamoto
Keyword(s):  
Shape Memory Alloys ◽  
Shape Memory ◽  
Parent Phase ◽  
Stacking Faults ◽  
Martensite Phase ◽  
Reverse Transformation ◽  
Aging Effects ◽  
Scanning Calorimetry ◽  
Martensite Stabilization ◽  
Cu And Zn

AbstractThe aging effects of two kinds of Cu-Zn-Al shape memory alloys (Cu-ll.4 Zn-18.7A1 (A) and Cu-ll.2Zn-17.lAl (B) in at%) have been examined by differential scanning calorimetry (DSC), transmission electron microscopy (TEM) and atom location by channeling enhanced microanalysis (ALCHEMI). In the directly quenched (D.Q.) state, alloy A was the parent phase, Ms being 253 K, and alloy B was the martensite phase. The alloy B was subjected another quenching treatment as follows: It was once quenched into an oil bath at 423 K and held for 300 s, followed by quenching into iced water (step quench (S.Q.) ). The D.Q. alloy B did not exhibit the reverse transformation because of a stabilization of the martensbite phase, but the S.Q. alloy B did and its As temperature of the reverse transformation was raised with the progress of aging at the martensitic state. Fraction of Zn atoms at the Cu(2) site examined by the ALCHEMI measurements was almost the same in the parent phase of D.Q. alloy A and its aged one, indicating no change in Cu and Zn atom sites, while it was gradually decreased in S.Q. alloy B with the progress of aging. The fraction of Zn atoms in D.Q. alloy B was much lower than those in the S.Q. alloy B and its aged one. TEM observation of the S.Q. alloy B revealed that stacking faults as the lattice invariant shear in the M18R martensites decreased in the density with the progress of aging. The decrease in the fraction of Zn atoms and in the density of stacking faults well corresponds to the increase in As temperature, and thus the martensite stabilization was attributed to a disordering between Cu and Zn atoms and to an annihilation of stacking faults.

New trends in differential scanning calorimetry

1989 ◽  
Vol 67 (6) ◽  
pp. 983-990 ◽  
Author(s):  
H. Tachoire ◽  
V. Torra
Keyword(s):  
Differential Scanning Calorimetry ◽  
Acoustic Emission ◽  
Martensitic Transformation ◽  
Shape Memory Alloys ◽  
Shape Memory ◽  
Phase Transformations ◽  
Entropy Production ◽  
Thermomechanical Treatment ◽  
Scanning Calorimetry

Recent applications of differential scanning calorimetry in the study of solid–solid transformations are presented. The importance of the deconvolution of the thermograms and of the modelling of the calorimetric equipment is stressed.Investigations of the phase transformations of the martensitic type in shape-memory alloys have made clear the influence of thermomechanical treatment of the material and have evaluated the influence of defects on the dynamics of transformation. A combination of calorimetric and acoustical observations has demonstrated irreversibilities, even in the so-called thermoelastic transitions. Keywords: martensitic transformation, differential scanning calorimetry, entropy production, thermomechanical treatments, acoustic emission.

scholarly journals Thermomechanical analysis of nitinol memory alloy behavior

2021 ◽  
Vol 102 (2) ◽  
pp. 161-167
Author(s):  
Nazarii Bykiv ◽  
Volodymyr Iasnii ◽  
Petro Yasniy ◽  
Robert Junga
Keyword(s):  
Strain Rate ◽  
Shape Memory ◽  
Phase Transformations ◽  
Functional Materials ◽  
Thermomechanical Analysis ◽  
Mechanical Tests ◽  
Scanning Calorimetry ◽  
External Temperature ◽  
Austenitic Transformation ◽  
Heating And Cooling

Shape memory alloys are functional materials characterized by the effect of shape memory and superelasticity. Due to these properties, they are widely used, particularly, in bioengineering, aeronautics, robotics and civil engineering. The temperatures of phase transformations and the influence of external temperature and strain rate on the functional and mechanical characteristics of Ni55.75Ti44.15 shape memory alloy are investigated in this paper. The temperature of alloy phase transformations is obtained by differential scanning calorimetry (DSC) in the temperature range from -70°C to 70°C. Diagrams of differential scanning calorimeters at different heating and cooling rates of Ni55.75Ti44.15 alloy is constructed and analyzed. Samples for mechanical tests are made of round rod 8 mm in diameter. The samples working area is 12.5 mm in length and 4 mm in diameter. Mechanical tests are carried out at temperatures close to the maximum value of the completion temperature of martensitic-austenitic transformation Af = 14.7°C. Diagrams of deformation under uniaxial tension are constructed and stresses of phase transformations, Young's modulus and relative elongations of transformation areas at different loading speeds and exterior temperatures are determined. Using Clausius-Clapeyron formula, it is shown that with simultaneous changes in temperature and strain rate, the stresses of phase transformations are largely due to changes in temperature rather than load rates. The coefficients of Clausius-Clapeyron equation for superelastic Ni55.75Ti44.15 alloy with shape memory, which are consistent with those known in the literature, are determined.

scholarly journals Behaviour of NiTi SMA Helical Springs under Different Temperatures and Deflections

2013 ◽  
Vol 2013 ◽  
pp. 1-4 ◽  
Author(s):  
R. Santhanam ◽  
Y. Krishna ◽  
M. S. Sivakumar
Keyword(s):  
Shape Memory ◽  
Smart Materials ◽  
Shape Recovery ◽  
Scanning Calorimetry ◽  
Helical Springs ◽  
Heating And Cooling ◽  
Niti Sma ◽  
Different Temperatures ◽  
Sma Spring ◽  
Sma Helical Spring

Shape memory alloys (SMAs) are one of the most widely used smart materials in many applications because of their shape memory effect property. In this work, the behaviour of NiTi SMA helical spring was evaluated through isothermal force-displacement experiment (IFDE) and shape recovery force experiment (SRFE). The transformation temperatures of SMA spring were determined by differential scanning calorimetry (DSC) test. In situ heating of SMA spring by direct electric current was used instead of conventional furnace heating. The continuous measurement of temperature of SMA spring during heating and cooling was ensured with attaching the thermocouple by heat shrinkable sleeve. From IFDE, the force-deflection behaviour under different constant temperatures and from SRFE and the force-temperature behaviour under different constant deflections are obtained. The results of IFDE show that the force increases and the residual displacement decreases with an increase in the temperature, and the stiffness of the spring at austenite state is greater than that at martensitic state. The results of SRFE show that the shape recovery force increases more or less linearly with an increase in the initial deflection for the same temperature range. But the shape recovery forces are not similar during heating and cooling stages. This paper presents the experimental setup, experimental procedures, and the observed behaviour of SMA helical springs under different temperatures and deflections.

Synthesis and Mesomorphic Properties of Three-Benzene-Ring Containing Bent-Core Liquid Crystal 1,3-Phenylene-bis[4-(nonylcarboyloxyl) benzylideneamine]

2010 ◽  
Vol 428-429 ◽  
pp. 79-82 ◽  
Author(s):  
Yuan Ming Huang ◽  
Qing Lan Ma ◽  
Bao Gai Zhai
Keyword(s):  
Phase Transition ◽  
Differential Scanning Calorimetry ◽  
Liquid Crystal ◽  
Benzene Ring ◽  
Cyclic Heating ◽  
Scanning Calorimetry ◽  
Polarized Optical Microscopy ◽  
Heating And Cooling ◽  
Phase Transition Temperatures ◽  
Mesomorphic Properties

A bent-core compound with three benzene-ring cores 1,3-phenylene-bis [4-(nonylcarboyloxyl)benzyl ideneamine] was synthesized. Its mesomorphic properties were characterized with differential scanning calorimetry and polarized optical microscopy, respectively. This kind of bent-core compound exhibited mesophases in the temperature range of 155-185oC for the first cooling but cyclic heating and cooling could lower the phase transition temperatures for this bent-core liquid crystal. Our results demonstrated that bent-core molecules with three benzene-ring cores can also form mesophases as those five benzene-ring containing bent-core molecules do.

scholarly journals Structural Characteristics of Multilayered Ni-Ti Nanocomposite Fabricated by High Speed High Pressure Torsion (HSHPT)

Metals ◽  
2020 ◽  
Vol 10 (12) ◽  
pp. 1629
Author(s):  
Gheorghe Gurau ◽  
Carmela Gurau ◽  
Francisco Manuel Braz Fernandes ◽  
Petrica Alexandru ◽  
Vedamanickam Sampath ◽  
...  
Keyword(s):  
High Pressure ◽  
Shape Memory ◽  
High Speed ◽  
High Pressure Torsion ◽  
Structural Characteristics ◽  
Nickel Titanium ◽  
Martensitic Transition ◽  
Scanning Calorimetry ◽  
Heating And Cooling ◽  
Electron Microscopes

It is generally accepted that severe plastic deformation (SPD) has the ability to produce ultrafinegrained (UFG) and nanocrystalline materials in bulk. Recent developments in high pressure torsion (HPT) processes have led to the production of bimetallic composites using copper, aluminum or magnesium alloys. This article outlines a new approach to fabricate multilayered Ni-Ti nanocomposites by a patented SPD technique, namely, high speed high pressure torsion (HSHPT). The multilayered composite discs consist of Ni-Ti alloys of different composition: a shape memory alloy (SMA) Ti-rich, whose Mf > RT, and an SMA Ni-rich, whose Af < RT. The composites were designed to have 2 to 32 layers of both alloys. The layers were arranged in different sequences to improve the shape recovery on both heating and cooling of nickel-titanium alloys. The manufacturing process of Ni-Ti multilayers is explained in this work. The evolution of the microstructure was traced using optical, scanning electron and transmission electron microscopes. The effectiveness of the bonding of the multilayered composites was investigated. The shape memory characteristics and the martensitic transition of the nickel-titanium nanocomposites were studied by differential scanning calorimetry (DSC). This method opens up new possibilities for designing various layered metal-matrix composites achieving the best combination of shape memory, deformability and tensile strength.

Phase Transformation in Ni-Ti Shape Memory and Superelastic Alloys Subjected to High Pressure Torsion

2010 ◽  
Vol 123-125 ◽  
pp. 1007-1010 ◽  
Author(s):  
Karimbi Koosappa Mahesh ◽  
Francisco M. Braz Fernandes ◽  
Gheorghe Gurau
Keyword(s):  
High Pressure ◽  
Phase Transformation ◽  
Shape Memory ◽  
High Pressure Torsion ◽  
X Ray Diffraction ◽  
Scanning Calorimetry ◽  
One Stage ◽  
Heating And Cooling ◽  
Ti Alloys ◽  
M Phase

A systematic study on the phase transformation of Ni-Ti shape memory and superelastic alloys subjected to Severe Plastic Deformation (SPD) – High Pressure Torsion (HPT) technique has been carried out. Ni-Ti alloys of three compositions were chosen for the study. Specimens of these alloys in as-received (AR) condition and after HPT have been subjected to Differential Scanning Calorimetry (DSC) and X-ray Diffraction (XRD) analyses. In this study, while comparing the results of DSC thermograms and XRD spectra for the same sample conditions, some differences were observed. In the case of NiTi-H alloy after HPT, there appeared one stage phase transformation with DSC both while heating and cooling suggesting Martensite↔Austenite transformation but, with respect to XRD spectra while cooling, at the intermediate temperature of 55°C, the R-phase peaks corresponding to (1 1 2)R and (3 0 0)R planes appeared. In the thermogram obtained for the NiTi-B alloy subjected to HPT, it is observed that, while cooling, the Austenite to R-phase transformation is merged with R-phase to Martensite transformation. The results of the XRD obtained at -180°C show the presence of R-phase along with M-phase. The DSC curve of the NiTi-S alloy subjected to HPT corresponds to one stage phase transformation both while heating and cooling but, the diffractogram of the sample obtained at -180°C corresponds to the presence of both R-phase and M-phase.

scholarly journals Effect of Nanofiller Content on Dynamic Mechanical and Thermal Properties of Multi-Walled Carbon Nanotube and Montmorillonite Nanoclay Filler Hybrid Shape Memory Epoxy Composites

Polymers ◽  
2021 ◽  
Vol 13 (5) ◽  
pp. 700
Author(s):  
Muhamad Hasfanizam Mat Yazik ◽  
Mohamed Thariq Hameed Sultan ◽  
Mohammad Jawaid ◽  
Abd Rahim Abu Talib ◽  
Norkhairunnisa Mazlan ◽  
...  
Keyword(s):  
Shape Memory ◽  
High Performance ◽  
Loss Modulus ◽  
Decomposition Temperature ◽  
Hybrid Nanocomposites ◽  
Mechanical And Thermal Properties ◽  
Scanning Calorimetry ◽  
Hybrid Filler ◽  
Dynamic Mechanical ◽  
Tan Δ

The aim of the present study has been to evaluate the effect of hybridization of montmorillonite (MMT) and multi-walled carbon nanotubes (MWCNT) on the thermal and viscoelastic properties of shape memory epoxy polymer (SMEP) nanocomposites. In this study, ultra-sonication was utilized to disperse 1%, 3%, and 5% MMT in combination with 0.5%, 1%, and 1.5% MWCNT into the epoxy system. The fabricated SMEP hybrid nanocomposites were characterized via differential scanning calorimetry, dynamic mechanical analysis, and thermogravimetric analysis. The storage modulus (E’), loss modulus (E”), tan δ, decomposition temperature, and decomposition rate, varied upon the addition of the fillers. Tan δ indicated a reduction of glass transition temperature (Tg) for all the hybrid SMEP nanocomposites. 3% MMT/1% MWCNT displayed best overall performance compared to other hybrid filler concentrations and indicated a better mechanical property compared to neat SMEP. These findings open a way to develop novel high-performance composites for various potential applications, such as morphing structures and actuators, as well as biomedical devices.

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