Signature of Austenitic to Martensitic Phase Transition in Ni2MnGa in Mn and Ni K-Edge XANES Spectra

The XANES studies at Mn, Ni and Ga K-edge of Ni2MnGa compound have been carried out at room and low temperatures. The Mn K-edge and Ni K-edge spectra shows modulation in the post edge features when the sample is cooled below martensitic transition temperature. It is strongly reflected in the XANES of Mn K-edge where the peak after the edge gets totally suppressed when the sample is in martensitic phase. This peak shows a hysteretic behaviour when thermal cycling was done across the martensitic transition temperature. This clearly shows that the peak height is a measure of austenitic phase present at a particular temperature. This demonstrates the strong correlations of electronic states and crystal structures in these compounds.

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Phase Transition in Iron Thin Films Containing Coherent Twin Boundaries: A Molecular Dynamics Approach

Materials ◽

10.3390/ma13163631 ◽

2020 ◽

Vol 13 (16) ◽

pp. 3631 ◽

Cited By ~ 1

Author(s):

Binjun Wang ◽

Yunqiang Jiang ◽

Chun Xu

Keyword(s):

Thin Films ◽

Phase Transition ◽

Molecular Dynamics ◽

Free Surface ◽

Transition Temperature ◽

Film Thickness ◽

Martensitic Phase ◽

Martensitic Transition ◽

Twin Boundaries ◽

Martensitic Phase Transition

Using molecular dynamics (MD) simulation, the austenitic and martensitic phase transitions in pure iron (Fe) thin films containing coherent twin boundaries (TBs) have been studied. Twelve thin films with various crystalline structures, thicknesses and TB fractions were investigated to study the roles of the free surface and TB in the phase transition. In the austenitic phase transition, the new phase nucleates mainly at the (112)bcc TB in the thicker films. The (111¯)bcc free surface only attends to the nucleation, when the film is extremely thin. The austenitic transition temperature shows weak dependence on the film thickness in thicker films, while an obvious transition temperature decrease is found in a thinner film. TB fraction has only slight influence on the austenitic temperature. In the martensitic phase transition, both the (1¯10)fcc free surface and (111)fcc TB attribute to the new body-center-cubic (bcc) phase nucleation. The martensitic transition temperature increases with decreased film thickness and TB fraction does not influent the transition temperature. In addition, the transition pathways were analyzed. The austenitic transition obeys the Burgers pathway while both the Kurdjumov–Sachs (K–S) and Nishiyama–Wassermann (N–W) relationship are observed in the martensitic phase transition. This work may help to understand the mechanism of phase transition in the Fe nanoscaled system containing a pre-existing defect.

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Martensite-austenite and Ferromagnetic-paramagnetic Transformations in Ni2-xAxMn1-yByGa1-zCz (A, B=Co; C=Al) Heusler Alloys

Revista de Chimie ◽

10.37358/rc.08.12.2058 ◽

2009 ◽

Vol 59 (12) ◽

Author(s):

Mihail-Liviu Craus ◽

Viorel Dobrea ◽

Mihai Lozovan

Keyword(s):

Magnetic Field ◽

Transition Temperature ◽

Martensitic Transformation ◽

Low Temperatures ◽

Room Temperature ◽

Heusler Alloys ◽

Partial Substitution ◽

Martensitic Transition ◽

Cscl Type ◽

Curie Temperatures

Ni2MnGa Heusler alloy is known as a potential smart material. At room temperature it has a L21 type structure, undergoing a martensitic transition (TM) at low temperatures. Some authors have classified Ni-Mn-Ga Heusler alloys on the values of martensitic transformation and Curie temperatures: first group formed by alloys with TM below room temperature and TC, second group with TM around room temperature and third group with TM]TC. The partial substitution of Ni with Mn leads to an increase of the transition temperature and a decrease of the Curie temperature. The Ni2-xMn1+xGa alloys have a complex tetragonal structure at room temperature. The substitution of Ga with Al can change the crystalline and magnetic structure of Heusler alloys: Ni2MnAl is antiferromagnetic for a B2 (CsCl type, with Mn and Al randomly distributed in the center of the cube) structure and ferromagnetic for a L21 (BiF3 type with Mn and Al ordered distributed in the cube center) structure. We intend to put in evidence a dependence between the applied magnetic field on a side, and the transition temperature, on other side, for the Ni2-xAxMn1-yByGa1-zCz (A, B=Co; C=Al) Heusler alloys.

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In situ Tensile Experiments at Low Temperatures on Niobium Single Crystals by H.V.E.M.

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100113913 ◽

1975 ◽

Vol 33 ◽

pp. 58-59

Author(s):

F. H. Louchet ◽

L. P. Kubin

Keyword(s):

Electron Microscope ◽

Transition Temperature ◽

Low Temperature ◽

Slip System ◽

Low Temperatures ◽

Tensile Axis ◽

Image Intensifier ◽

Screw Dislocations ◽

Source Operation

Experiments have been carried out on the 3 MeV electron microscope in Toulouse. The low temperature straining holder has been previously described Images given by an image intensifier are recorded on magnetic tape.The microtensile niobium samples are cut in a plane with the two operative slip directions [111] and lying in the foil plane. The tensile axis is near [011].Our results concern:- The transition temperature of niobium near 220 K: at this temperature and below an increasing difference appears between the mobilities of the screw and edge portions of dislocations loops. Source operation and interactions between screw dislocations of different slip system have been recorded.

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Martensitic phase transition

Physics Subject Headings (PhySH) ◽

10.29172/901531cd-56c5-438f-9b88-5096ac032655 ◽

2018 ◽

Keyword(s):

Phase Transition ◽

Martensitic Phase ◽

Martensitic Phase Transition

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Features of radiothermoluminescence of polypropylene and ethylene propylenediene elastomer SKEPT-4044 compositions with nanoscale metal-containing fillers

Physics and Chemistry of Materials Treatment ◽

10.30791/0015-3214-2020-3-66-73 ◽

2020 ◽

pp. 66-73

Author(s):

A.M. Magerramov ◽

◽

N.I. Kurbanova ◽

M.N. Bayramov ◽

N.A. Alimirzoyeva ◽

...

Keyword(s):

Transition Temperature ◽

Molecular Mobility ◽

Fe3o4 Nanoparticles ◽

Low Temperatures ◽

Frost Resistance ◽

Relaxation Processes ◽

Ethylene Propylene ◽

Temperature Range ◽

Β Relaxation

Using radiothermoluminescence (RTL), the molecular mobility features in the temperature range of 77-300 K were studied for the polypropylene (PP)/ethylene propylene diene elastomer SKEPT-4044 with NiO, Cu2O and Fe3O4 nanoparticles (NPs) based on ABS-acrylonitrile butadiene or SCS-divinyl styrene matrices. It has been shown that the introduction of nanofillers in PP significantly affects the nature and temperature of γ- and β-relaxation processes, while the region of manifestation of the β-process noticeably shifts to the region of low temperatures. Composites with Cu2O NPs have a higher β-transition temperature Tβ than composites with other NPs. It was found that PP/SKEPT-4044 composites with Cu2O NPs with a dispersion of 11-15 nm and acrylonitrile butadiene thermoplastics have optimal frost resistance compared to other compositions.

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Electron Irradiation of YBa2Cu3O7 at low Temperatures

MRS Proceedings ◽

10.1557/proc-99-491 ◽

1987 ◽

Vol 99 ◽

Cited By ~ 8

Author(s):

B. Stritzker ◽

W. Zander ◽

F. Dworschak ◽

U. Poppe ◽

K. Fischer

Keyword(s):

Transition Temperature ◽

Electron Irradiation ◽

Normal State ◽

Low Temperatures ◽

Superconducting Transition Temperature ◽

Superconducting Transition ◽

Radiation Induced ◽

State Resistance ◽

Normal State Resistance

ABSTRACTBulk samples of YBa2Cu3O7−x have been homogenously irradiated with 3 MeV electrons at temperatures below 20 K. Whereas the superconducting transition temperature, Tc, drops dramatically with increasing dose the width of the transition remains unchanged (Δ Tc ≤ 1.5 K). The normal state resistance at 100 K increases substantially during the electron irradiation. Several irreproducible experiments can be interpreted with a radiation induced, unstable increase of Tc.

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