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1
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Structural and Morphological Investigations on Shape Memory CuZnAl Alloys

100%
Zengin R., Kayal N.
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issue 4
619-622
EN
Macroscopic, structural and morphological features of shape memory CuZnAl alloys were examined by elongation parameter measurement, X-ray diffraction and optical metallography. It has been seen that shape initiating temperature (T_{z}) is greater than austenite start temperature (A_{s}). According to the X-ray diffraction, it has been defined that transformation happened from austenite phase to martensite phase as L2_1 → M18R and martensite crystal lattice has been in monoclinic structure. In metallographic observations the grain structures were observed, then plate martensites, V-type martensite structures, twin-like bands, precipitation phases were found. In addition, it has been observed that α-sediment phase has occurred in specimens with ageing at austenitic phase condition.
2
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Magnetic Characterization of Melt-Spun Co-Ni-Ga Ferromagnetic Superelastic Alloy

100%
Mino J., Ipatov M., Gamcova J., Saksl K., Durisin M., Zhukova V., Vargova Z., Zhukov A., Varga R.
Acta Physica Polonica A
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2017
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vol. 131
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issue 4
1075-1077
EN
Ribbons of composition Co₄₉Ni₂Ga₃₀ have been prepared by melt-spinning method. X-ray diffraction investigation revealed single phase with B2 structure at room temperature. However, analysis of magnetization dependence of temperature suggests phase transition in the range 150-250 K. Resistivity measurements revealed similar transition with shift to higher temperatures in the presence of magnetic field.
3
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Controlling of Transformation Temperatures of Cu-Al-Mn Shape Memory Alloys by Chemical Composition

63%
Aksu Canbay C., Karagoz Z., Yakuphanoglu F.
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vol. 125
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issue 5
1163-1166
EN
The Cu-Al-Mn shape memory alloys having various chemical compositions were prepared by arc melting method to control the phase transformation parameters. The phase transformation parameters and structural properties of the alloys were investigated by differential scanning calorimetry and optic microscopy, respectively. The effects of the chemical composition on characteristic transformation temperatures, enthalpy and entropy values of Cu-Al-Mn ternary system were investigated. The characteristic transformation temperatures of austenite and martensite phase (A_{s}, A_{f}, M_{s}, and M_{f}) are increased with change in the chemical composition of the alloys. The average crystallite size for the alloys was calculated to determine the effect of aluminum and manganese compositions on the transformation temperatures. The change in transformation temperatures indicates the same trend with change in crystallite size. The obtained results suggest that the phase transformation parameters of the Cu-Al-Mn alloys can be controlled by Al and Mn contents.
4
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Characterization of Superelastic NiTi Alloys by Nanoindentation: Experiments and Simulations

63%
Frost M., Kruisová A., Sháněl V., Sedlák P., Haušild P., Kabla M., Shilo D., Landa M.
Acta Physica Polonica A
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2015
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vol. 128
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issue 4
664-669
EN
NiTi-based shape memory alloys are metallic materials exhibiting remarkable response to mechanical and/or thermal loading, e.g. superelasticity, pseudoplasticity or one-way shape memory effect. They can be engineered into structures of micro-size dimensions, hence, they appear promising for application in micro-electromechanical systems. For their efficient utilization, appropriate characterization is important. Due to relative simplicity, indentation represents a very standard and popular technique for basic characterization of metallic materials providing information about stiffness and hardness. Moreover, it can be used for identification of other events in the material. This study aims to verify applicability of the recently developed constitutive model for NiTi-based shape memory alloy in simulations of nanoindentation tests. The model is fitted to a particular sample material using experimental data, and a series of simulations mimicking tests at various temperatures is performed. Since the model also captures two-stage martensitic transformation via the intermediate R-phase, its influence on the simulations is investigated as well. It is confirmed that spherical indentation is a suitable method for simple and fast detection whether the material is in superelastic or pseudoplastic regime.
5
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Martensite Reorientation after Thermal Cycling in NiTiCu Shape Memory Alloys Studied by EBSD Technique

63%
Rak J., Goryczka T., Ochin P.
Acta Physica Polonica A
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2016
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vol. 130
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issue 4
1075-1078
EN
The Ni₂₅Ti₅₀Cu₂₅ shape memory alloy exhibits one-step martensitic transformation. Transformation occurs between the B2 parent phase and the B19 orthorhombic martensite. The course of the martensitic transformation was in situ studied in the alloy with use of electron backscatter diffraction. During heating, reverse martensitic transformation occurs from the B19 orthorhombic martensite to the B2 parent phase. On cooling, from the parent phase the B19 martensite is formed. Obtained results proved that the B19 martensitic plates forms the variants indexed as 1, 3, and 5. Thermal cycling does not change the crystallographic correlation between the parent phase and the martensite. However, after cycling, different rearrangement of the martensitic plates can be received. In consequence, characteristic temperatures of the martensitic transformation are shifted.
6
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TiPd Shape Memory Alloy Studied by PAC Method

63%
Kulińska A., Wodniecki P.
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vol. 125
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issue 4
936-939
EN
Perturbed angular correlation (PAC) method was applied to study the martensitic phase transition of the TiPd shape memory alloy doped with In, Hf, and Zr. The hyperfine interaction parameters and their concentration and temperature dependences for ^{111}In/^{111}Cd and ^{181}Hf/^{181}Ta probe atoms were determined. The influence of ternary element additions on the electric field gradients at Pd site was evidenced. A decrease of the martensite start temperature (M_{S}) and an increase of the width of the hysteresis loop (T_{H}) with an increasing concentration of the impurities in TiPd alloy was observed. These relationships are much stronger for In and Zr, than for Hf admixture.
7
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Thermo-Mechanical Properties of an NiTi-Shape Memory Alloy after Dynamic Loading

51%
Grigorieva V., Danilov A., Razov A.
Acta Physica Polonica A
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2015
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vol. 128
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issue 4
592-596
EN
The results of the comparative study of a quasi-equilibrium NiTi alloy's thermo-mechanical response to high-rate and quasi-static straining in the temperature range of 100-300°C, which included the A_{f} and the M_{d} temperatures, are considered. The existence of B2 → B19' and B2 → R → B19' martensitic transformations, associated with the heterogeneous distribution of Ni₄Ti₃ precipitates is shown to result in shaping of martensitic and austenitic two-way shape memories, the simultaneous presence of which determines the reversing shape memory effect. The suppression of stress-induced B2 → B19' transformation at temperatures higher than the M_{d} temperature resulted in austenitic two-way shape memory only. Distinct dependences on the temperature of the critical stresses that initiate B2 → B19' and B2 → R → B19' martensitic transformations in austenite are shown to be the reason for the participation of the irreversible mechanisms of straining at the earliest stages of tension, whatever the strain-rate applied, thus annihilating the distinctions between the quasi-static and high-rate straining processes. As a result, the thermo-mechanical properties acquired after tension become practically independent of the strain-rate.
8
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Structure of Metal Oxide Multilayers Deposited by Sol-Gel Method on Surface of NiTi Shape Memory Alloy

51%
Osak P., Waś J., Łosiewicz B.
Acta Physica Polonica A
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2016
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vol. 130
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issue 4
1069-1071
EN
The metal oxide layers were deposited onto the surface of NiTi shape memory alloy using sol-gel method. Single-, double- and triple-layers were obtained from a colloidal solution containing the precursor of zirconium tetrabutoxide and titanium tetrabutoxide, and annealed at 300°C for 1 h in argon. Phase composition was determined by grazing incidence X-ray diffraction. Surface roughness of the metal oxide layers were determined by atomic force microscopy. Surface morphology and thickness of the obtained layers were studied by scanning electron microscopy. It was found that all obtained layers revealed a composite structure, and were characterized by low surface roughness and thickness parameters. A homogeneous structure of the metal oxide layers deposited onto the surface of the medical NiTi alloy was ascertained only for double- and triple-layers.
9
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X-Ray Diffraction Studies of the Reversible Phase Transformation in NiTi Shape Memory Alloy

51%
Lekston Z., Zubko M.
Acta Physica Polonica A
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2016
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vol. 130
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issue 4
1059-1062
EN
In the present paper the phase transformations occurring in hot worked and heat-treated Ni-rich NiTi shape memory alloy were studied using X-ray diffraction, differential scanning calorimetry and bend and free recovery measurements. Based on conducted measurements it can be seen that in the studied alloy two-step B2 ↔ R ↔ B19' phase transitions occurred. Due to the fact that during heating the phase transition B2 → R and R → B19' occurs in a very narrow temperature range and differential scanning calorimetry peaks overlap additional X-ray diffraction measurements were performed. Obtained characteristic temperatures from applied different experimental methods are in good agreement. The optimum heat-treatment was selected to obtain rods with a shape recovery temperature A_{f} below 37°C to prepare prototypes of medical implants activated by patients body heat.
10
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Structure and Properties of NiTi Shape Memory Alloy after Cold Rolling in Martensitic State

51%
Świec P., Zubko M., Lekston Z., Stróż D.
Acta Physica Polonica A
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2016
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vol. 130
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issue 4
1081-1084
EN
Due to unique features, like shape memory effects and superelasticity, NiTi alloys with nearly equiatomic composition are used in various branches of industry. Application of severe plastic deformation can drastically change properties of the materials. In the present paper the Ni_{50.4}Ti_{49.6} alloy after cold rolling in the martensitic state and further annealed is studied. Phase transformations were studied using X-ray diffraction and differential scanning calorimetry measurements. Microstructure was examined using transmission electron microscopy and electron backscattering diffraction methods. Mechanical properties of obtained alloys has been studied using Vickers microhardness tests. Based on the performed measurements it can be seen that in studied alloys two steps B2 ↔ R ↔ B19' phase transitions occurred. Performed plastic deformation influences course of phase transitions and phases composition. Due to the reduction of grain size microhardness of the studied material is increasing with increase of deformation degree.
11
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Local Pseudoelastic Behaviour and Surface Characteristics of N Ion Implanted NiTi Shape Memory Alloy

51%
Levintant-Zayonts N., Kwiatkowski L., Swiatek Z., Brzozowska J.
Acta Physica Polonica A
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2017
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vol. 132
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issue 2
210-216
EN
The main goal of the proposed paper is to present the results of the nitrogen ion implantation effects on mechanical and corrosion properties of NiTi shape memory alloy. Local pseudoelasticity phenomena of NiTi were determined using the ultra-low load applied system. The load-penetration depth curves show that lower nitrogen fluence improves mechanical properties in the near surface layer but higher ion fluence leads to degradation of pseudoelasticity properties. Corrosion resistance of NiTi in the Ringer solution was evaluated by means of electrochemical methods. The results of potentiodynamic measurements in the anodic range for implanted NiTi indicate a decrease of passive current density range in comparison with non-treated NiTi, without any signs related to Ni release. The results of impedance measurements recorded at the corrosion potential show a capacitive behaviour for all samples without clear predominance of one of them. It can be explained by the fact that this result concerns the first stage of corrosion exposition. It is shown that nitrogen ion implantation leads to formation of modified surface of improved physicochemical properties.
12
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Influence of High Fluence Nitrogen Ion Implantation οn Pseudoelastic Behaviour of NiTi Shape Memory Alloy

51%
Levintant-Zayonts N., Kucharski S.
Acta Physica Polonica A
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2011
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vol. 120
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issue 1
79-82
EN
An attempt to evaluate mechanical properties changes (superelastic phenomena) in the shape memory NiTi alloy (austenitic form) due to ion implantation (N^{+}, fluences of 1 × 10^{17} and 4 × 10^{18} cm^{-2}) has been made. We applied the differential scanning calorimetry technique and spherical indentation (micro- and nanoindentation scale) test to study superelastic effect. The results of investigations of selected functional properties, i.e. characteristic temperatures, total and recovered penetration depth on the implanted and non-implanted NiTi samples are presented.
13
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NiTi Shape Memory Marformed Alloy Studied by Electron Beam Precession TEM Orientation Mapping Method

38%
Świec P., Zubko M., Lekston Z., Stróż D.
Acta Physica Polonica A
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2017
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vol. 131
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issue 5
1307-1310
EN
Severe plastic deformation by cold-rolling in martensitic state was applied to Ni_{50.4}Ti_{49.6} shape memory alloy. Received materials with 17, 20, 25, and 35% deformation were further annealed at 450°C for 15 min. After such treatment hardness of this alloy increased significantly reaching 365 HV0.5 for highest deformation degree. Calorimetric studies revealed two-stage and two-step character of martensitic transformation occurring in all specimens. Nanocrystalline structure with average grain size 53, 34, 28, and 24 nm was obtained. In material with 35% of deformation amorphous regions containing a nuclei of B2 parental phase with average size of 5 nm were observed. To determine the crystallographic orientation of observed nanograins and for better phase analysis, electron beam precession transmission electron microscopy orientation mapping was performed.
14
Content available remote

On Analysis of DSC Curves for Characterization of Intrinsic Properties of NiTi Shape Memory Alloys

38%
Ziółkowski A.
Acta Physica Polonica A
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2012
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vol. 122
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issue 3
601-605
EN
Differential scanning calorimetry is discussed as a tool for characterization of shape memory alloy materials with the example of Ni_{51at.%}-Ti polycrystalline material. Some inconsistencies connected with the differential scanning calorimetry analysis results present in the contemporary literature are indicated, for example large discrepancies in the registered heats of phase transition or differences in registered heats of forward and reverse phase transition, especially in the case of multi-stage phase transition sequences. An attempt is undertaken to explain some of the discrepancies. The overall conclusion from the present work is that forward and reverse sensible heats of phase transition are equal, and discrepancies reported in the literature are artefacts. It is recommended that as a standard practice of differential scanning calorimetry analysis of shape memory alloy materials not only characteristic temperatures but also sensible heat of phase transition should be reported, which can be done at practically no additional cost.
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