@{MTMT:34576321, title = {Kinetics of Surface Segregation in Alloys: Formation of Metastable States with Anti-Phase Boundaries Near the Surface}, url = {https://m2.mtmt.hu/api/publication/34576321}, author = {Beke, Dezső and Cserháti, Csaba}, booktitle = {Advances in Physical Metallurgy}, doi = {10.1201/9781003424000-46}, unique-id = {34576321}, year = {2023}, pages = {360-367} } @article{MTMT:33786706, title = {Acoustic emission and DSC investigations of anomalous stress-stain curves and burst like shape recovery of Ni49Fe18Ga27Co6 shape memory single crystals}, url = {https://m2.mtmt.hu/api/publication/33786706}, author = {Kamel, Sarah M. and Daróczi, Lajos and Tóth, László Zoltán and Panchenko, Elena and Chumljakov, Yuriy I. and Mohareb, Nora Samy Sdky and Beke, Dezső}, doi = {10.1016/j.intermet.2023.107932}, journal-iso = {INTERMETALLICS}, journal = {INTERMETALLICS}, volume = {159}, unique-id = {33786706}, issn = {0966-9795}, abstract = {Simultaneous acoustic emission, AE, and DSC measurements under compression along [110]A direction were carried out on Ni49Fe18Ga27Co6 shape memory single crystals. The compression resulted in anomalous stressstrain loops with stress drops/jumps on it, reflecting a sudden formation/dissolution of a more stable (detwinned) martensite structural modification than the thermally induced (twinned) one. The final detwinned martensite, obtained below a certain temperature, was stable even after downloading: during heating it showed a burst-like recovery at about 35K higher transformation temperature than that of the thermally induced one, with an audible click. It was obtained that the number of acoustic events showed strong asymmetry: e.g. for stress induced transformations the number of hits for uploading was larger. Simultaneous measurements of stress-time curves and AE versus time revealed that in the nucleation/dissolution processes in both (up and down) directions, as an intermediate step, the twinned martensite was first formed and resulted in additional AE events. This was interpreted by the easy as well as difficult nucleation of the twinned and detwinned martensites, respectively. The stress drops on the uploading stress-strain curve were attributed to subsequent nucleation of the detwinned martensite from the twinned modification and were followed by a sharp decrease of the AE activity. This indicated that the formation of detwinned martensite is a sudden, fast process and can take place without significant elastic energy storage. This was also in agreement with the fact that during burst like thermal recovery the width of the transition was very small (Af ≅ As). Similarly, during downloading the stress jumps were interpreted as sudden dissolutions of the detwinned phase by retwinning and at all stress jumps there were local maxima on the AE activity curve.}, keywords = {differential scanning calorimetry; Martensitic transformation; shape-memory alloy; Martensitic microstructure; Shape-memory Effect; martensitic structure; acoustic emission spectroscopy}, year = {2023}, eissn = {1879-0216}, orcid-numbers = {Panchenko, Elena/0000-0002-2769-6090} } @article{MTMT:33745669, title = {Scaling of Average Avalanche Shapes for Acoustic Emission during Jerky Motion of Single Twin Boundary in Single-Crystalline Ni2MnGa}, url = {https://m2.mtmt.hu/api/publication/33745669}, author = {Tóth, László Zoltán and Bronstein, Emil and Daróczi, Lajos and Shilo, Doron and Beke, Dezső}, doi = {10.3390/ma16052089}, journal-iso = {MATERIALS}, journal = {MATERIALS}, volume = {16}, unique-id = {33745669}, abstract = {Temporal average shapes of crackling noise avalanches, U(t) (U is the detected parameter proportional to the interface velocity), have self-similar behavior, and it is expected that by appropriate normalization, they can be scaled together according to a universal scaling function. There are also universal scaling relations between the avalanche parameters (amplitude, A, energy, E, size (area), S, and duration, T), which in the mean field theory (MFT) have the form E∝A3, S∝A2, S∝T2. Recently, it turned out that normalizing the theoretically predicted average U(t) function at a fixed size, U(t)=atexp−bt2 (a and b are non-universal, material-dependent constants) by A and the rising time, R, a universal function can be obtained for acoustic emission (AE) avalanches emitted during interface motions in martensitic transformations, using the relation R~A1−φ too, where φ is a mechanism-dependent constant. It was shown that φ also appears in the scaling relations E~A3−φ and S~A2−φ, in accordance with the enigma for AE, that the above exponents are close to 2 and 1, respectively (in the MFT limit, i.e., with φ= 0, they are 3 and 2, respectively). In this paper, we analyze these properties for acoustic emission measurements carried out during the jerky motion of a single twin boundary in a Ni50Mn28.5Ga21.5 single crystal during slow compression. We show that calculating from the above-mentioned relations and normalizing the time axis of the average avalanche shapes with A1−φ, and the voltage axis with A, the averaged avalanche shapes for the fixed area are well scaled together for different size ranges. These have similar universal shapes as those obtained for the intermittent motion of austenite/martensite interfaces in two different shape memory alloys. The averaged shapes for a fixed duration, although they could be acceptably scaled together, showed a strong positive asymmetry (the avalanches decelerate much slower than they accelerate) and thus did not show a shape reminiscent of an inverted parabola, predicted by the MFT. For comparison, the above scaling exponents were also calculated from simultaneously measured magnetic emission data. It was obtained that the φ values are in accordance with theoretical predictions going beyond the MFT, but the AE results for φ are characteristically different from these, supporting that the well-known enigma for AE is related to this deviation.}, year = {2023}, eissn = {1996-1944} } @article{MTMT:33539708, title = {Thermodynamic Analysis of Anomalous Shape of Stress–Strain Curves for Shape Memory Alloys}, url = {https://m2.mtmt.hu/api/publication/33539708}, author = {Beke, Dezső and Kamel, S.M. and Daróczi, Lajos and Tóth, László Zoltán}, doi = {10.3390/ma15249010}, journal-iso = {MATERIALS}, journal = {MATERIALS}, volume = {15}, unique-id = {33539708}, year = {2022}, eissn = {1996-1944} } @article{MTMT:33205595, title = {Clustering Characterization of Acoustic Emission Signals Belonging to Twinning and Dislocation Slip during Plastic Deformation of Polycrystalline Sn}, url = {https://m2.mtmt.hu/api/publication/33205595}, author = {Tóth, László Zoltán and Daróczi, Lajos and Elrasasi, T.Y. and Beke, Dezső}, doi = {10.3390/ma15196696}, journal-iso = {MATERIALS}, journal = {MATERIALS}, volume = {15}, unique-id = {33205595}, year = {2022}, eissn = {1996-1944} } @article{MTMT:33051601, title = {Denouement of the Energy-Amplitude and Size-Amplitude Enigma for Acoustic-Emission Investigations of Materials}, url = {https://m2.mtmt.hu/api/publication/33051601}, author = {Kamel, S.M. and Mohareb, Nora Samy Sdky and Tóth, László Zoltán and Daróczi, Lajos and Beke, Dezső}, doi = {10.3390/ma15134556}, journal-iso = {MATERIALS}, journal = {MATERIALS}, volume = {15}, unique-id = {33051601}, abstract = {There are many systems producing crackling noise (avalanches) in materials. Temporal shapes of avalanches, U(t) (U is the detected voltage signal, t is the time), have self-similar behaviour and the normalized U(t) function (e.g., dividing both the values of U and t by S-1/2 , where S is the avalanche area), averaged for fixed S, should be the same, independently of the type of materials or avalanche mechanisms. However, there are experimental evidences that the temporal shapes of avalanches do not scale completely in a universal way. The self-similarity also leads to universal power-law-scaling relations, e.g., between the energy, E, and the peak amplitude, A(m), or between S and A(m). There are well-known enigmas, where the above exponents in acoustic emission measurements are rather close to 2 and 1, respectively, instead of E similar to A(m)(3) and S similar to A(m)(2), obtained from the mean field theory, MFT. We show, using a theoretically predicted averaged function for the fixed avalanche area, U(t)= at exp(-bt(2)) (where a and b are non-universal, material-dependent constants), that the scaling exponents can be different from the MFT values. Normalizing U by A(m) and t by t(m) (the time belonging to the A(m): rise time), we obtain tm similar to A(m)(1-phi) (the MFT values can be obtained only if phi would be zero). Here, phi is expected to be material-independent and to be the same for the same mechanism. Using experimental results on martensitic transformations in two different shape-memory single-crystals, phi = 0.8 +/- 0.1 was obtained (phi is the same for both alloys). Thus, dividing U by A(m) as well as t by A(m)(1-phi) (similar to t(m)) leads to the same common, normalized temporal shape for different, fixed values of S. This normalization can also be used in general for other experimental results (not only for acoustic emission), which provide information about jerky noises in materials.}, keywords = {Acoustic emission; Shape memory alloys; Scaling relations; temporal shapes of avalanches}, year = {2022}, eissn = {1996-1944} } @article{MTMT:32602494, title = {Change of acoustic emission characteristics during temperature induced transition from twinning to dislocation slip under compression in polycrystalline sn}, url = {https://m2.mtmt.hu/api/publication/32602494}, author = {Daróczi, Lajos and Elrasasi, T.Y. and Arjmandabasi, T. and Tóth, László Zoltán and Veres, B. and Beke, Dezső}, doi = {10.3390/ma15010224}, journal-iso = {MATERIALS}, journal = {MATERIALS}, volume = {15}, unique-id = {32602494}, year = {2022}, eissn = {1996-1944} } @article{MTMT:32289901, title = {Tracking Twin Boundary Jerky Motion at Nanometer and Microsecond Scales}, url = {https://m2.mtmt.hu/api/publication/32289901}, author = {Bronstein, Emil and Tóth, László Zoltán and Daróczi, Lajos and Beke, Dezső and Talmon, Ronen and Shilo, Doron}, doi = {10.1002/adfm.202106573}, journal-iso = {ADV FUNCT MATER}, journal = {ADVANCED FUNCTIONAL MATERIALS}, volume = {Epub}, unique-id = {32289901}, issn = {1616-301X}, keywords = {Barkhausen noise; AVALANCHES; Shape memory alloys; Twin boundary; materials mechanics}, year = {2021}, eissn = {1616-3028}, pages = {1-11} } @article{MTMT:31625545, title = {Optimized Size and Distribution of Silver Nanoparticles on the Surface of Titanium Implant Regarding Cell Viability}, url = {https://m2.mtmt.hu/api/publication/31625545}, author = {Hajdu, Péter and Lampé, István and Rácz, Richárd Péter and Biri, Sándor and Csík, Attila and Tóth, Ferenc and Szalóki, Melinda and Hegedűs, V and Dombrádi, Zsuzsanna Rita and Varga, István and Csarnovics, István and Kökényesi, Sándor Jenő and Beke, Dezső and Hegedűs, Csaba}, doi = {10.3390/app10207063}, journal-iso = {APPL SCI-BASEL}, journal = {APPLIED SCIENCES-BASEL}, volume = {10}, unique-id = {31625545}, year = {2020}, eissn = {2076-3417}, orcid-numbers = {Csík, Attila/0000-0002-8173-9653; Szalóki, Melinda/0000-0002-7052-0322} } @article{MTMT:31609701, title = {Formation of ordered L10-FePt phase in FePt–Ag thin films}, url = {https://m2.mtmt.hu/api/publication/31609701}, author = {Makushko, P.V. and Shamis, M.N. and Schmidt, N.Y. and Kotenko, I.E. and Gulyás, Szilvia and Katona, Gábor and Verbytska, T.I. and Beke, Dezső and Albrecht, M. and Makogon, I.M.}, doi = {10.1007/s13204-020-01552-2}, journal-iso = {APPL NANOSCI}, journal = {APPLIED NANOSCIENCE}, volume = {10}, unique-id = {31609701}, issn = {2190-5509}, abstract = {In this work, the influence of an Ag layer, which is located at different positions of the layer stack (top, intermediate, bottom), on the structural and magnetic properties of orderedL1(0)phase in Fe(50)Pt(50)films was investigated. It was found that the position of an additional Ag layer affects the stress state of the as-deposited FePt films. Mechanical stress is induced during deposition and post-annealing process due to the difference in thermal expansion coefficients and lattice mismatch of FePt, Ag, and substrate. The initial stress state affects the ordering process during subsequent heat treatment. The higher level of initial compressive stress (- 7.8 GPa) in FePt/Ag/FePt films results inL1(0)phase formation at a temperature of 700 degrees C which is about 100 degrees C lower than in films with Ag bottom (- 3.6 GPa) and top (+ 0.86 GPa) layers. A more pronounced (001) oriented growth of theL1(0)phase was observed in stacks with Ag top layer as compared to Ag bottom and intermediate layers. The highest values of coercivity were obtained for films with Ag intermediate and bottom layers, which is due to the distribution of Ag along FePt grain boundaries that result in strong exchange decoupling of FePt grains. Furthermore, the formation of the orderedL1(0)phase at comparatively low temperatures of about 370 degrees C was observed in a free-standing FePt/Ag (30 nm)/FePt film.}, keywords = {annealing; COERCIVITY; Ordering; Stress state; L1(0)-FePt phase}, year = {2020}, eissn = {2190-5517}, pages = {4809-4816} }