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1
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Two-Step Martensitic Transformation in an Aged Ti_{50}Ni_{15}Pd_{25}Cu_{10} High Temperature Shape Memory Alloys

100%
Rehman S., Khan M., Nusair Khan A., Ali L., Imran Jaffery S.
Acta Physica Polonica A
|
2015
|
vol. 128
|
issue 2B
B-125-B-127
EN
Multi-step martensitic transformation in an aged Ni-rich binary NiTi shape memory alloy is considered as usual behavior during transformation from austenite to martensite phase; from (austenite) B2 to R-phase and then R-phase to B19' (monoclinic). However, for equi-atomic NiTi-based quaternary high temperature shape memory alloy, two-step martensitic transformation was detected for the first time. The Ti_{50}Ni_{15}Pd_{25}Cu_{10} high temperature shape memory alloys were investigated for the evolution of transformation temperatures at aging temperature of 550°C and 700°C. Aging at 550°C for 6 h resulted in significant reduction of phase transformation temperatures. During forward transformation from austenite to martensite, two-step martensitic transformation B2 → R and R → B19 (orthorhombic) was observed. By aging the alloy at 700°C for 6 h, no significant effect was found on phase transition behavior and transformation temperatures.
2
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Influence of Fe Addition on the Martensitic Transformation, Structure and Magnetic Properties of Metamagnetic Ni-Co-Mn-Sn Alloys

63%
Wójcik A., Maziarz W., Szczerba M., Sikora M., Hawełek Ł., Czaja P.
Acta Physica Polonica A
|
2016
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vol. 130
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issue 4
1026-1028
EN
In this study the effect of Fe for Ni substitution in Ni₄₄Co₆Mn₃₉Sn₁₁ metamagnetic shape memory alloys on their structure, magneto-structural transformation characteristics, magnetic and magnetocaloric properties was studied. The results show that the structure and martensite transformation behavior strongly depends on the Fe concentration. The martensitic transformation temperature decreases with 1 at.% of Fe and is suppressed with higher Fe content. It was further found that substitution of Fe for Ni leads to lowering of the value of magnetic entropy change.
3
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Strained Tetragonal Bain Paths in Fe_{3}Pt Invar

63%
Pugaczowa-Michalska M., Lipiński S.
Acta Physica Polonica A
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2000
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vol. 97
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issue 5
749-752
EN
Employing the LMTO-ASA method we calculated the total energy variation of Fe_{3}Pt along the tetragonal distortion path connecting fcc and bcc structures for isotropic biaxial path and uniaxially strained path and compare the results with energies for the unstrained path.
4
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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
|
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.
5
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Surface Hardening of Ductile Cast Iron by Electrolytic Plasma Technology

51%
Ayday A., Durman M.
Acta Physica Polonica A
|
2013
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vol. 123
|
issue 2
291-293
EN
Traditional surface modification obligations, surface coatings, and other methods of surface treatment are used to increase the hardness and mechanical properties of specimen surfaces. But those techniques are limited due to the high equipment cost, and material consumption. Electrolytic plasma technology is a special heat treatment process employing electrolysis in an aqueous solution under particular conditions, for instance voltage, current, electrolyte, duration, and heating-quenching rate. In this study, surface modification of GGG70 cast iron was carried out by using electrolytic plasma treatment. Certain voltage and ampere values were performed to obtain good surface properties. Metallographic studies were carried out with an optical microscope to study the hardened and modified surfaces. The effect of impulse time on surface temperature was investigated and it was observed that the temperature on the workpiece increased with increasing impulse time. It was found that the electrolytic plasma treatment could significantly increase hardness of the cast iron.
6
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Martensitic Transformation in Co-Based Ferromagnetic Shape Memory Alloy

51%
Kopeček J., Yokaichiya F., Laufek F., Jarošová M., Jurek K., Drahokoupil J., Sedláková-Ignácová S., Molnár P., Heczko O.
Acta Physica Polonica A
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2012
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vol. 122
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issue 3
475-477
EN
The Co_{38}Ni_{33}Al_{29} alloy in both powder and bulk state was investigated in the presented study using neutron diffraction on E9 high resolution powder diffractometer at HZB (BER II). The reverse martensitic phase transformation from the tetragonal martensitic phase into the cubic austenitic phase was observed with the phase coexistence within the temperatures from 183 K to 133 K. The fcc cobalt solid solution particles distributed in the transforming matrix remained in the same state through the whole temperature range. The obtained results agree with magnetization measurements on the same annealed sample. The powder data are compared with experiments on bulk sample, although there was a texture present. The obtained results provide further information about the phase transition process in this important class of ferromagnetic shape memory alloys.
7
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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
|
2016
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vol. 130
|
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.
8
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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
|
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.
9
Content available remote

Martensitic Transformations and Magnetic Properties of Ni-Mn-Sn Heusler Alloy Films

51%
Dubowik J., Szlaferek A., Gościańska I.
Acta Physica Polonica A
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2008
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vol. 113
|
issue 1
163-168
EN
We report on structural and magnetic properties of Ni_{50}Mn_{50-x}Sn_x (x=12÷14) films and compare them with those of the bulk Ni-Mn-Sn alloys. Magnetic measurements reveal clear presence of martensitic transformation in bulk alloys but in the flash-evaporated Ni-Mn-Sn thin films martensitic transformation is usually less visible. The best film samples annealed for 1 h at about 900 K exhibit clear signs of martensitic transformation: i.e., a small defect in magnetization and a substantial increase in ferromagnetic resonance line width.
10
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The Application of Laboratory X-Ray Micro-Diffraction to Study the Effects of Clinching Process in Steel Sheets

51%
Krztoń H., Mucha J., Witkowski W.
Acta Physica Polonica A
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2016
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vol. 130
|
issue 4
985-987
EN
The application of X-ray micro-diffraction to study the local changes in austenite content in clinching joints made of DP 600 steel is presented. The relations between various parameters of the cold pressing process and the microstructure and the austenite content in the individual parts of the clinching joints are shown.
11
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Monitoring of Heat Treatment Processes by High Energy Synchrotron Radiation

51%
Klemradt U., Rieger T., Herrmann K., Carmele D., Meyer S., Lippmann T., Stark A., Bleck W.
Acta Physica Polonica A
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2012
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vol. 121
|
issue 1
39-43
EN
Advanced engineering materials are frequently based on multiphase microstructures, where the decisive step is the heat treatment adjusting the desired microstructure. A typical example are transformation-induced plasticity assisted steels, where the steel grades depend on the phase composition and the deformation-induced transformation of retained austenite into martensite. Usually methods for microstructural characterization are only applied after completion of the heat treatment process and comprise typically microscopy and X-ray analysis with laboratory tubes. Both methods can suffer from artefacts and probe a relatively small surface or volume, respectively. However, in the last decade synchrotron facilities have become available that offer very hard X-rays, which open up new possibilities for the observation of heat treatment processes owing to the unique combination of extremely high intensities with large penetration depths (mm scale). Sophisticated sample environments allow for complex in situ experiments, currently with a time resolution on the order of seconds. Only recently a commercial dilatometer of type Bähr Dil805AD has become available at the HARWI-2 beamline at the HASYLAB. This experimental setup was used for the in situ investigation of the quenching and partitioning process in transformation-induced plasticity steels. The experiments were performed in transmission at a wavelength of 0.0124 nm. The Debye-Scherrer rings were observed arising from statistical grain distributions characteristic for each microstructure. The time-resolved measurements allow conclusions about the phases present in the sample, their lattice parameters, texture and grain size.
12
Content available remote

Spin Disordered Resistivity of the Heusler Ni₂MnGa-based Alloys

51%
Kamarád J., Kaštil J., Albertini F., Fabbrici S., Arnold Z.
Acta Physica Polonica A
|
2017
|
vol. 131
|
issue 4
1072-1074
EN
Electrical resistivity of the selected Heusler off-stoichiometric (NiCo)₂Mn(GaIn) alloys was studied in a wide range of temperature and magnetic field. A step-like change of resistivity (Δρ ≈24 μΩcm) was detected in the off-stoichiometric Ni_{1.85}Mn_{1.21}Ga_{0.94} alloy at temperature of martensitic structural transition. This Δρ is much more significant than one in the stoichiometric Ni₂MnGa alloy. In the case of the off-stoichiometric (NiCo)₂Mn(GaIn) alloys, an enormous change of resistivity, Δρ ≈ 200 μΩcm, accompanies the structural transition. Simultaneously, the maximum of the spin disordered resistivity ρ_{sd}(T) of austenite phase of the alloys is slightly dependent on composition of the alloy and vary from ≈30 μΩcm up to ≈45 μΩcm, in good agreement with theoretical calculations. Due to high sensitivity of the structural transition temperature of the alloys to magnetic field, the very pronounced magnetoresistance effects have been observed in the studied alloys.
13
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The Evolution of Microstructure for Ductile Iron Treated under Different Thermal Cycles Using Electrolytic Plasma Treatment

45%
Ayday A., Durman M.
|
|
vol. 125
|
issue 2
577-578
EN
The effects of the thermal cycles on the microstructures and properties of ductile iron modified by electrolytic plasma treatment were investigated. Microstructure changes occurring in the modified surface were characterized with scanning electron microscopy, X-ray diffractometry techniques. Martensitic structure evolved in the heat affected zone and ledeburite structure was produced in the molten zone of the ductile iron. Microhardness of the treated specimens improved considerably as compared to the original sample. X-ray diffraction clearly revealed the formation of a martensite phases in the modified zone.
14
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Structure of Chitosan-ZnO Layers Electrophoretically Deposited on NiTi Shape Memory Alloy

45%
Goryczka T., Kokoszka A., Kowalski P., Łosiewicz B.
Acta Physica Polonica A
|
2016
|
vol. 130
|
issue 4
1056-1058
EN
The surface of NiTi shape memory was modified by deposition of chitosan-ZnO thin film. The electrodeposition process was carried out at room temperature at voltage-time conditions: 10 V/30 s, 10 V/300 s, 20 V/30 s, or 20 V/300 s. Structure of the obtained coatings was studied by means of grazing incidence beam X-ray diffraction. Distribution of the zinc oxide particles in the chitosan matrix was observed with use of scanning electron microscopy. It was found that depending on the electrodeposition parameters, the structure of the obtained chitosan-ZnO coatings varies from amorphous to coarse-grained.
15
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Magnetic Properties and Structure of the Ni-Co-Mn-In Alloys with the Boron Addition

45%
Prusik K., Matyja E., Kubisztal M., Zubko M., Swadźba R.
Acta Physica Polonica A
|
2017
|
vol. 131
|
issue 5
1240-1243
EN
Series of Ni_{45.5-x}Co_{4.5}Mn_{36.6}In_{13.4}B_{x} (at.%, x=0, 0.05, 0.1, 0.5, 1.0) polycrystalline magnetic shape memory alloys were examined in terms of the magnetic properties, structure and transition temperatures. Depending on the boron concentration single or two phase alloys microstructures were observed. Additionally, the martensitic transformation temperatures decreases with the boron addition. Magnetic-field induced transformation occurs for the alloys with the boron addition up to 0.1 at.%. For alloys with 0.5 and 1.0 at.% of B transformation is hindered.
16
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Structure of the Extruded and Thermally Treated Ni_{54.3}Fe_{16.2}Ga_{29.5} Alloy

38%
Prusik K., Matyja E., Zubko M., Goryczka T.
Acta Physica Polonica A
|
2016
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vol. 130
|
issue 4
1020-1022
EN
Hot extrusion process was applied to Ni_{54.3}Fe_{16.2}Ga_{29.5} polycrystalline alloy. Then the rod was annealed subsequently for 1 h at 700, 800, 900, and 1100°C. In this paper the effect of annealing on the microstructure of the polycrystalline extruded Ni-Fe-Ga alloy were analyzed. The structure of the alloys was determined by the X-ray and transmission electron microscopy. The electron backscattering diffraction technique was applied to obtain the texture of the extruded rods after heat treatment.
17
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.
18
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Effect of Deformation on the Transformation Temperatures of Martensite and Bainite Structures in Cu-9.97%Al-4.62%Mn Alloy

38%
Aldirmaz E.
Acta Physica Polonica A
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2016
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vol. 129
|
issue 1
40-42
EN
At present study of Cu-9.97%Al-4.62%Mn alloy system is used. Some physical properties of martensitic and bainite phase transformatios in Cu-9.97%Al-4.62%Mn (wt%) alloy were investigated by means of scanning electron microscopy and differential scanning calorimetry. In scanning electron microscope observations of Cu-9.97%Al-4.62%Mn alloy were noted two kinds of martensitic phases. These phases were defined as β'₁ (M18R) and γ'₁ (2H) martensites structures. According to differential scanning calorimetry measurement results, the deformation induced temperature is expected to be higher than the thermally induced temperature in Cu-9.97%Al-4.62%Mn alloy for martensite and bainite structures.
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