Microstructure, Phase Stability, Mechanical Properties, and Shape Memory Characteristics of Ni-Fe-AI-B Alloys

1991 ◽  
Vol 246 ◽  
Author(s):  
E. P. George ◽  
C. T. Liu ◽  
C. J. Sparks ◽  
Ming-Yuan Kao ◽  
J. A. Horton ◽  
...  
Keyword(s):  
Shape Memory ◽  
Room Temperature ◽  
Cold Work ◽  
Second Phase ◽  
Scanning Calorimetry ◽  
Two Phase ◽  
Transformation Temperatures ◽  
Plate Morphology ◽  
Hot Rolled ◽  
Memory Characteristics

AbstractConventionally cast and hot-rolled Ni-Fe-AI-B alloys containing 4-20 at.% Fe, 23.9- 31.5 at.% Al, and 300 wppm B were investigated in this study. After oil quenching from 1300°C, all the alloys—except SMA-15 (27A1-14Fe)—have at least a two-phase microstructure, one phase of which is martensite with the characteristic plate morphology, and the other a globular second phase distributed throughout the microstructure. The amount of second phase generally increases with increasing Fe content. Alloys containing less than 14% Fe were found to be quite brittle at room temperature, indicating that a ductile second phase is at least partly responsible for the improved room-temperature ductility in the high-Fe alloys. The best tensile ductility (12%) was obtained in SMA-17 (23.9AI-20Fe) which was shown by X-ray diffraction to consist of 40% (mostly disordered) fcc [(Ni,Fe)3 (AI,Fe)] + 30% (partly ordered) bct martensite + 30% B2. Differential scanning calorimetry showed that the transformation temperatures for this alloy were MP = 65°C and AP = 95°C. Room-temperature tensile strains of 2-3% could be almost completely recovered in SMA-17 by heating for 3 min. at 600°C with the load removed. Upon subsequent cycling (i.e., strain-anneal cycling), the amount of strain recovery increased dramatically from 70% in the first cycle to nearly 100% after 4-5 cycles, indicating that cold work may help in improving the shape memory characteristics of this alloy. SMA-15 was found to have significantly higher transformation temperatures (Mp = 143°C and Ap = 170°C) than SMA-17; however, it is relatively brittle compared to SMA-17.

Effect of Aging Treatment on Phase Transformation of a Pseudoelastic NiTi Alloy

2014 ◽  
Vol 936 ◽  
pp. 1216-1223 ◽  
Author(s):  
Palloma Viera Muterlle ◽  
Eduard Benavides Villamarin ◽  
Paulo Herrera ◽  
Edson Paulo da Silva
Keyword(s):  
Phase Transformation ◽  
Shape Memory ◽  
Room Temperature ◽  
Niti Alloy ◽  
Aging Treatment ◽  
Single Step ◽  
Treatment Temperature ◽  
Scanning Calorimetry ◽  
Transformation Temperatures ◽  
X Ray

The pseudoelasticity (PE) and shape memory effect (SME) are the two main behaviors presented by the shape memory alloys (SMA's) and are associated respectively to mechanical and thermally induced martensitic transformations. The aim of this work is to investigate the effects of heat treatment temperature on the microstructure properties and phase transformation temperatures of a NiTi alloy with 57 w.t. % Ni. The X-ray diffraction (XRD) was carried out to obtain the phases present. The phase transformation temperatures were measured by differential scanning calorimetry (DSC). The alloy chemical composition and hardness were obtained by X-ray fluorescence (XRF), hardness (HRC) and microhardness (HV) tests, respectively. The analysis were performed in the state as received and after aging treatment at different temperatures between 350 °C and 600°C. The samples as received contained a fully austenitic microstructure at room temperature and the DSC analysis showed the presence of a phase transformation in multiple steps (B19'-R-B2). After aging at 350 °C the R phase was observed at room temperature with the austenite. With the aging treatment at 600 °C the R phase was solubilized and the alloy phase transformation occurred in a single step, ie, direct transformation from austenite to martensite and vice versa. The transformation temperatures Af, As, Ms and Mf changed with the aging treatment temperatures.

scholarly journals Textural Modifications during Recovery in Ti-Rich Ni-Ti Shape Memory Alloy Subjected to Low Level of Cold Work Reduction

2010 ◽  
Vol 636-637 ◽  
pp. 618-623 ◽  
Author(s):  
Andersan S. Paula ◽  
Karimbi Koosappa Mahesh ◽  
Norbert Schell ◽  
Francisco Manuel Braz Fernandes
Keyword(s):  
Shape Memory ◽  
Phase Transformations ◽  
Room Temperature ◽  
Cold Work ◽  
Strain Curve ◽  
X Ray Diffraction ◽  
Stress Strain Curve ◽  
Scanning Calorimetry ◽  
Low Level ◽  
Physical And Mechanical Characteristics

In shape memory alloys (SMA), the texture can be an interesting factor influencing the anisotropic physical and mechanical characteristics during the phase transformations. It is well known that the texture significantly influences the stress-strain curve and shape memory strain of NiTi SMA. The aim of the present experiment was to analyze the textural modifications in the Ti-rich Ni-Ti SMA after annealing at moderate (500°C for 30 min) and subsequent low level of cold work reduction (10% thickness reduction). The textural results were obtained by X-Ray Diffraction (XRD) during thermal cycling in three points: (i) at room temperature (B19’ phase, after cold work), (ii) at 180°C (B2 phase), and (iii) at room temperature (B19’ phase, after cooling from 180°C). The phase transformations were characterized by Differential Scanning Calorimetry (DSC) and XRD.

NiTi Shape Memory Alloy Used for Multiple-Resetting Actuator for Fire Protection

2017 ◽  
Vol 907 ◽  
pp. 8-13 ◽  
Author(s):  
Lucian Burlacu ◽  
Nicanor Cimpoeşu ◽  
Nicoleta Monica Lohan ◽  
Leandru Gheorghe Bujoreanu
Keyword(s):  
Thermal Analysis ◽  
Shape Memory Alloy ◽  
Shape Memory ◽  
Fire Protection ◽  
Room Temperature ◽  
Parent Phase ◽  
Niti Shape Memory Alloy ◽  
Scanning Calorimetry ◽  
Protection Systems ◽  
Executive Elements

The paper introduces the possibility to replace the “wet alloy”, used for sprinkler-triggering within automatic fire protection systems, with a shape memory alloy (SMA) type. The idea of the present application is based on the thermoelastic reversible martensitic transformation, governing SMA functioning, which has completely reversible character, and enables the occurrence of two-way shape memory effect (TWSME) after the application of a thermomechanical treatment called “training”. For this purpose a commercial NiTi rod, which was martensitic at room temperature, was subjected to thermal analysis tests, performed by differential scanning calorimetry (DSC) and dilatometry. Martensite (M) reversion to parent phase (A), during heating, was emphasized by an endothermic peak on the DSC thermogram and by a length shrinkage, on the dilatogram. The capacity to develop TWSME was revealed by the change in displacement-temperature variation, with increasing the number of training cycles. This stabilized fully reversible behavior recommends NiTi rods as executive elements of a new concept of resettable sprinkler for fire protection.

Structural Characterization of Co70-xNixGa30 Ferromagnetic Shape Memory Alloys

2008 ◽  
Vol 52 ◽  
pp. 103-108 ◽  
Author(s):  
Sidananda Sarma ◽  
A. Srinivasan
Keyword(s):  
Magnetic Susceptibility ◽  
Shape Memory ◽  
Room Temperature ◽  
Structural Parameters ◽  
Ac Magnetic Susceptibility ◽  
X Ray Diffraction ◽  
Ferromagnetic Shape Memory Alloys ◽  
Two Phase ◽  
X Ray ◽  
Ferromagnetic Shape Memory

Polycrystalline ingots of Co70–xNixGa30 (20 ≤ x ≤ 26) ferromagnetic shape memory alloy (FSMA) were prepared by arc melting elemental powders followed by homogenization at 1230 °C for 24 hrs and quenching in liquid nitrogen. Room temperature X-Ray diffraction (XRD) patterns of as-quenched samples exhibited single-phase tetragonal structure for alloy compositions with x = 21 to 26, and a two-phase structure (cubic A2-phase along with weak tetragonal phase) for the alloy with x = 20. Rietveld refinement was performed on the X-ray diffraction patterns to obtain the refined structural parameters. Differential Scanning Calorimeter (DSC) curves recorded from 30 °C to 250 °C revealed martensite-austenite and austenite-martensite transformations in all alloys except the alloy with composition x = 20. Low temperature ac magnetic susceptibility measurements confirmed the existence of martensitic transformations in the alloy with x = 20. The structural transformation temperatures show a linear variation with e/a ratio. All the alloys were ferromagnetic at room temperature. Curie temperature was determined using a high temperature ac magnetic susceptibility measurement set-up.

Investigation of Ageing Phenomena in CuAlNi Based Shape Memory Alloys

2007 ◽  
Vol 537-538 ◽  
pp. 129-136 ◽  
Author(s):  
Marton Benke ◽  
Valéria Mertinger ◽  
E. Nagy ◽  
Jan Van Humbeeck
Keyword(s):  
Martensitic Transformation ◽  
Shape Memory Alloys ◽  
Shape Memory ◽  
Ternary Alloy ◽  
Room Temperature ◽  
Beta Phase ◽  
Heat Treatments ◽  
Thermoelastic Martensitic Transformation ◽  
Transformation Temperatures ◽  
Exothermic Process

The ageing phenomena and its effect on the thermoelastic martensitic transformation was investigated in three Cu-base SMAs. The transformation temperatures shifted to higher temperatures due to aging in the beta-phase. To increase the alloy’s ductility, a definite amount of Mn (4 wt%) and Fe (2 wt%) were added to the ternary alloy. The thermoelastic martensitic transformation was found in the not-aged samples of the CuAlNiMn and CuAlNiMnFe alloys. This transformation was destroyed due to ageing heat treatments by a fairly unknown exothermic process. The thermoelastic martensitic transformation appeared again in the aged CuAlNiMn and CuAlNiMnFe samples after keeping them on room temperature for a few months. This phenomena was investigated by DSC, SEM, TEM, and XRD.

THE INCREASE OF THE MARTENSITIC DEFORMATION DURING SHAPE MEMORY EFFECT IN DEFORMED TiNi

2012 ◽  
Vol 05 (01) ◽  
pp. 1250011 ◽  
Author(s):  
GEORGIY FIRSTOV ◽  
YURI KOVAL ◽  
ALEKSANDR LOTKOV ◽  
VICTOR GRISHKOV ◽  
JAN VAN HUMBEECK
Keyword(s):  
Thermal Treatment ◽  
Shape Memory ◽  
Volume Fraction ◽  
Niti Alloy ◽  
Structure Refinement ◽  
External Stress ◽  
Low Temperature Annealing ◽  
Ultrafine Structure ◽  
Hot Rolled ◽  
Memory Characteristics

The evolution of the ultrafine structure, obtained at thermal treatment below recrystallization, and its effect onto shape memory characteristics in NiTi alloy was under study. It was shown that low temperature annealing (< 0.5 Tmelt) of the hot rolled NiTi leads to the structure refinement accompanied by the growth in accumulated martensite deformation. It was suggested that this is possible due to the increase of the volume fraction of martensite crystals properly oriented in respect to external stress.

MÖssbauer Study of a Tinife Shape Memory Alloy.

1991 ◽  
Vol 246 ◽  
Author(s):  
M. Jimenez ◽  
V. Marquina ◽  
S. Aburto ◽  
M.L. Marquina ◽  
R. Gomez ◽  
...  
Keyword(s):  
Mössbauer Spectroscopy ◽  
Shape Memory ◽  
Room Temperature ◽  
Mossbauer Spectroscopy ◽  
Density Wave ◽  
Quadrupole Doublet ◽  
Mössbauer Study ◽  
Scanning Calorimetry ◽  
Mößbauer Spectroscopy ◽  
Wave Induced

AbstractMÖssbauer spectroscopy is very sensitive to structural transitions that may occur during a phase change of the type known to arise in the shape memory TiNiFe alloy. In this work we present the results of resistance vs temperature, differential scanning calorimetry (DSC) and Mössbauer spectroscopy (MS) measurements in Ti50Ni47Fe3 sample. The resistance vs temperature curve shows the usual sharp increase associated to the B2 → R transition at Tp = 245 K and then raises until a maximum is attained at ∼ 150 K. The DSC curve shows a peak maximum at the same temperature where the resistivity starts to increase. The room temperature Mössbauer spectrum consists of a single line, indicating that the iron atoms have cubic surroundings. As temperature is lowered, a small asymmetric quadrupole doublet begins to develop. The isomer shift (I.S.) and quadrupole splitting (ΔQ) values of this doublet increase with decreasing temperature until almost constant values are achieved at temperatures ∼ 100 K. We relate the changes in the Mössbauer spectra with previously proposed charge density wave induced premartensitic transition.

Shape Memory Behavior and Mechanical Properties of NiMn and Ni(Mn,X) Alloys

1991 ◽  
Vol 246 ◽  
Author(s):  
W.S. Yang ◽  
D.E. Mikkola
Keyword(s):  
Mechanical Properties ◽  
Transition Temperature ◽  
Shape Memory ◽  
Room Temperature ◽  
Shape Recovery ◽  
Transformation Temperatures ◽  
Room Temperature Ductility ◽  
Substitutional Solute ◽  
Ternary Element ◽  
High Transition

AbstractPotential high transition temperature shape memory alloys based on NiMn have been studied with emphasis on the shape recovery, transformation temperatures and mechanical properties. Binary NiMn, which has been reported to be brittle, has a low shape recovery, but this can be increased with Al or Ti additions. Also, the transformation temperature can be changed and the room temperature ductility improved by ternary element additions. The various substitutional solute characteristics affecting the shape recovery, the transformation temperatures, and the ductility have been examined.

scholarly journals Microstructural characterization of Cu82.3Al8.3Mn9.4 shape memory alloy after rolling

10.30544/314 ◽  
2017 ◽  
Vol 23 (3) ◽  
pp. 281-289
Author(s):  
Mirko Gojić ◽  
Stjepan Kožuh ◽  
Ivana Ivanić ◽  
Magdalena Selanec ◽  
Tamara Holjevac Grgurić ◽  
...  
Keyword(s):  
Heat Treatment ◽  
Shape Memory Alloy ◽  
Cold Rolling ◽  
Shape Memory ◽  
Microstructural Characterization ◽  
Rolling Process ◽  
Scanning Calorimetry ◽  
Two Phase ◽  
Hot And Cold Rolling

In this paper, the microstructure of Cu82.3Al8.3Mn9.4 (in wt. %) shape memory alloy after hot and cold rolling was investigated. The Cu82.3Al8.3Mn9.4 alloy was produced by a vertical continuous casting method in the form a cylinder rod of 8 mm in diameter. After the casting, hot and cold rolling was performed. By hot rolling a strip with a thickness of 1.75 mm was obtained, while by cold rolling a strip with a thickness of 1.02 mm was produced. After the rolling process, heat treatment was performed. Heat treatment was carried out by solution annealing at 900 °C held for 30 minutes and water quenched immediately after heating. The microstructure characterization of the investigated alloy was carried out by optical microscopy (OM), scanning electron microscopy (SEM) equipped with a device for energy dispersive spectroscopy (EDS). Phase transformation temperatures and fusion enthalpies were determined by differential scanning calorimetry (DSC) method. The homogenous martensite microstructure was confirmed by OM and SEM micrographs after casting. During rolling the two-phase microstructure occurred. Results of DSC analysis showed martensite start (Ms), martensite finish (Mf), austenite start (As) and austenite finish (Af) temperatures.

Aging Effects in Ni-36% Al Shape Memory Alloy

1991 ◽  
Vol 246 ◽  
Author(s):  
David R. Angst ◽  
Ming-Yuan Kao ◽  
Bryan L. McKinney
Keyword(s):  
Differential Scanning Calorimetry ◽  
Precipitation Hardening ◽  
Al Alloys ◽  
Aging Effects ◽  
Scanning Calorimetry ◽  
Austenitic Phase ◽  
Transformation Temperatures ◽  
Microhardness Testing ◽  
Hot Rolled ◽  
Initial Peak

AbstractSamples of Ni-36 at% Al which were hot rolled, then solutionized at 1230°C and quenched, exhibited reversible transformations between the low-temperature, martensitic phase and the high temperature, austenitic phase. The initial peak transformation temperatures on heating (AP), cooling (MP), and the heats of transformation (ΔH) determined by differential scanning calorimetry (DSC) were ∼121°C, 119°C and 4 J/g, respectively for the as-solutionized material.Decreases in transformation temperatures and heats after aging at 350°C were also determined using differential scanning calorimetry (DSC), and microhardness testing (DPH). The DPH values plotted against age time showed two distinct peaks, a result similar to precipitation hardening in other Al alloys.

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