Influence of Multi-Axial Isothermal Forging on the Stability of Martensitic Transformation in a Heusler Ni-Mn-Ga Alloy

2021 ◽  
Author(s):  
I. I. Musabirov ◽  
I. M. Safarov ◽  
R. M. Galeyev ◽  
D. D. Afonichev ◽  
R. Y. Gaifullin ◽  
...  
Keyword(s):  
Martensitic Transformation ◽  
Isothermal Forging ◽  
The Stability

The Stability of Magnetic-Field-Induced Strain in a NiMnGa Ferromagnetic Shape Memory Alloy

2005 ◽  
Vol 475-479 ◽  
pp. 2025-2028
Author(s):  
Feng Chen ◽  
Zhiyong Gao ◽  
Wei Cai ◽  
Lian Cheng Zhao
Keyword(s):  
Magnetic Field ◽  
Martensitic Transformation ◽  
Twin Boundary ◽  
Boundary Mobility ◽  
Martensitic Transformation Temperature ◽  
Ferromagnetic Shape Memory Alloy ◽  
Field Cycling ◽  
The Stability ◽  
Increasing Temperature ◽  
Ferromagnetic Shape Memory

The stability of magnetic field induced strain (MFIS) in Ni52Mn24Ga24 single crystal under temperature and magnetic field cycling is investigated and the corresponding micro-mechanism is also discussed. It shows that the saturated MFIS is very sensitive to temperature. Below martensitic transformation temperature(Tm), with increasing temperature, the saturated MFIS increases almost linearly. Besides, the saturated MFIS initially decreases with increasing the field cycling number less than four times, then does not change with further increasing the number of field cycles. The decrease of saturated MFIS can be attributed to the decrease of twin boundary mobility, which is related to the crystal defect introduced by immigration of twin boundary under field cycling.

Role of Interstitial Oxygen Atom on Martensitic Transformation of Ti-Nb Alloy

2016 ◽  
Vol 97 ◽  
pp. 115-118
Author(s):  
Masaki Tahara ◽  
Tomonari Inamura ◽  
Hee Young Kim ◽  
Shuichi Miyazaki ◽  
Hideki Hosoda
Keyword(s):  
Martensitic Transformation ◽  
Oxygen Content ◽  
Martensite Phase ◽  
Interstitial Oxygen ◽  
Scanning Calorimetry ◽  
Martensite Stabilization ◽  
Oxygen Addition ◽  
The Stability ◽  
Effect Of Oxygen

The effect of oxygen content on the stability of α′′ martensite phase of the Ti-20mol%Nb alloy was investigated by differential scanning calorimetry. The reverse martensitic transformation temperature increased with increasing oxygen content, and this means that α′′ martensite phase was stabilized by oxygen addition. The mechanism of α′′ martensite stabilization by oxygen atoms was discussed based on the changes in the lattice parameters of α′′ martensite.

The role of chromium during austempering of ductile iron

2020 ◽  
Vol 117 (1) ◽  
pp. 104
Author(s):  
Arnoldo Bedolla-Jacuinde ◽  
Román Angel Hernandez-Hernandez ◽  
Francisco Vapeani Guerra ◽  
Ignacio Mejia
Keyword(s):  
Martensitic Transformation ◽  
Ductile Iron ◽  
Stage I ◽  
Stage Ii ◽  
Final Structure ◽  
Chromium Addition ◽  
Processing Window ◽  
Optimal Processing ◽  
The Stability

The present work analyzes the effect of small additions of chromium in the final structure of a commercial Austempered Ductile Iron (ADI). The study is made with emphasis on the effect of this element on the processing window. The results indicate that chromium addition decreases the stability of austenite promoting the martensitic transformation during cooling which increases the hardness and reduces the elongation. Likewise the increase in chromium addition delays the rate of transformation to ausferrite (stage I) and accelerates the stage II reaction promoting the bainite formation narrowing the optimal processing window. However, this effect is markedly reduced when the material is subjected to a long process of homogenization, prior to austempering process. The results of this work are discussed in terms of the degree of chromium segregation during solidification.

Stability of Ti-Ta Base High Temperature Shape Memory Alloys

2012 ◽  
Vol 706-709 ◽  
pp. 1921-1924 ◽  
Author(s):  
Hee Young Kim ◽  
Takafumi Kanaya ◽  
Tatsuhito Fukushima ◽  
Pio John S. Bueconsejo ◽  
Shuichi Miyazaki
Keyword(s):  
High Temperature ◽  
Martensitic Transformation ◽  
Thermal Cycling ◽  
Shape Memory ◽  
Transformation Temperature ◽  
Aging Effect ◽  
Cyclic Stability ◽  
Martensitic Transformation Temperature ◽  
Shape Memory Properties ◽  
The Stability

The stability of shape memory properties was investigated by thermal cycling tests in Ti-23Ta-(2-4)Sn alloys. The martensitic transformation temperature decreased considerably after aging at 573 K for the Ti-23Ta-2Sn alloy. The decrease in the martensitic transformation temperature by the aging effect was suppressed by the addition of 3at.%Sn and more to the Ti-23Ta alloy. The Ti-23Ta-3Sn alloy exhibited better cyclic stability compared with a Ti-32Ta alloy which has a similar transformation temperature.

Anomalies in Physical Properties Related to the Stability of the B2-Phase in Ti-Ni-Co Shape Memory Alloys

2005 ◽  
Vol 475-479 ◽  
pp. 1977-1982 ◽  
Author(s):  
Mi Seon Choi ◽  
Takashi Fukuda ◽  
Tomoyuki Kakeshita
Keyword(s):  
Electrical Resistivity ◽  
Magnetic Susceptibility ◽  
Martensitic Transformation ◽  
Specific Heat ◽  
Nucleation And Growth ◽  
Electronic Specific Heat ◽  
Transformation Behavior ◽  
First Order ◽  
The Stability ◽  
Specific Heat Coefficient

Martensitic transformation behavior of a series of Ti-(50-x)Ni-xCo at% alloys (x = 4, 8, 12, 16, 20) has been examined by electrical resistivity, magnetic susceptibility and specific heat measurements, in order to know the phase stability of the B2-type structure. The 4Co and 8Co alloys exhibit a typical first order B2-R-B19' transformation. The 12Co alloy probably transforms to the R-phase, but its microstructure is composed of small domains with about 10 nm in diameter, being quite different from the microstructure of a typical R-phase formed by nucleation and growth. The 16Co and the 20Co alloys do not show any martensitic transformation but anomalies of the electrical resistivity and magnetic susceptibility being similar to those of the 12Co alloy appear in these alloys. The diffuse scattering of 1/3<110> is also observed in the 16Co alloy. The Debye temperature decreases and electronic specific heat coefficient increases with increasing Co content.

scholarly journals Анизотропия термического расширения поликристаллического сплава системы Ni-Mn-Ga, подвергнутого пластической деформации ковкой

2018 ◽  
Vol 60 (6) ◽  
pp. 1051
Author(s):  
И.И. Мусабиров ◽  
И.М. Сафаров ◽  
Р.М. Галеев ◽  
Р.А. Гайсин ◽  
В.В. Коледов ◽  
...  
Keyword(s):  
Thermal Expansion ◽  
Phase Transformation ◽  
Bimodal Distribution ◽  
Structural Studies ◽  
Alloy Structure ◽  
Isothermal Forging ◽  
Bimodal Structure ◽  
Grain Sizes ◽  
Geometric Size ◽  
The Stability

AbstractThe formation of a sharp crystallographic texture in a Ni–Mn–Ga Heusler alloy by the multiple isothermal forging has been studied. An analysis of the thermal expansion near the martensitic transformation temperatures in the as-cast and forged states of the alloy shows that the thermomechanical treatment leads to an increase in the anisotropy of the sample geometric size changing during the phase transformation, which favors an increase in the functional characteristics of the alloy. The structural studies show that the alloy structure after multiple isothermal forging has the bimodal distribution of grain sizes. The formation of the bimodal structure by forging is assumed to make it possible to enhance the stability of the functional properties of the alloy during repeated cycles of the phase transformation.

Open discussion

1982 ◽  
Vol 99 ◽  
pp. 605-613
Author(s):  
P. S. Conti
Keyword(s):  
Buenos Aires ◽  
Large Mass ◽  
List Type ◽  
Common Phenomenon ◽  
Open Discussion ◽  
The Stability ◽  
Ring Nebulae

Conti: One of the main conclusions of the Wolf-Rayet symposium in Buenos Aires was that Wolf-Rayet stars are evolutionary products of massive objects. Some questions:–Do hot helium-rich stars, that are not Wolf-Rayet stars, exist?–What about the stability of helium rich stars of large mass? We know a helium rich star of ∼40 MO. Has the stability something to do with the wind?–Ring nebulae and bubbles : this seems to be a much more common phenomenon than we thought of some years age.–What is the origin of the subtypes? This is important to find a possible matching of scenarios to subtypes.

Symmetric Multistep Methods Revisited: II. Numerical Experiments

1999 ◽  
Vol 173 ◽  
pp. 309-314 ◽  
Author(s):  
T. Fukushima
Keyword(s):  
Multistep Methods ◽  
Computational Time ◽  
Integration Time ◽  
Implicit Methods ◽  
Symmetric Methods ◽  
Celestial Bodies ◽  
The Stability ◽  
Predictor Corrector ◽  
Symmetric Multistep Methods ◽  
Integration Errors

AbstractBy using the stability condition and general formulas developed by Fukushima (1998 = Paper I) we discovered that, just as in the case of the explicit symmetric multistep methods (Quinlan and Tremaine, 1990), when integrating orbital motions of celestial bodies, the implicit symmetric multistep methods used in the predictor-corrector manner lead to integration errors in position which grow linearly with the integration time if the stepsizes adopted are sufficiently small and if the number of corrections is sufficiently large, say two or three. We confirmed also that the symmetric methods (explicit or implicit) would produce the stepsize-dependent instabilities/resonances, which was discovered by A. Toomre in 1991 and confirmed by G.D. Quinlan for some high order explicit methods. Although the implicit methods require twice or more computational time for the same stepsize than the explicit symmetric ones do, they seem to be preferable since they reduce these undesirable features significantly.

Uniformity of Magnification from Different Electron Microscopes

1967 ◽  
Vol 25 ◽  
pp. 32-33
Author(s):  
Godfrey C. Hoskins ◽  
V. Williams ◽  
V. Allison
Keyword(s):  
Diffraction Grating ◽  
The Other ◽  
Carbon Replica ◽  
Electron Microscopes ◽  
The Stability

The method demonstrated is an adaptation of a proven procedure for accurately determining the magnification of light photomicrographs. Because of the stability of modern electrical lenses, the method is shown to be directly applicable for providing precise reproducibility of magnification in various models of electron microscopes.A readily recognizable area of a carbon replica of a crossed-line diffraction grating is used as a standard. The same area of the standard was photographed in Phillips EM 200, Hitachi HU-11B2, and RCA EMU 3F electron microscopes at taps representative of the range of magnification of each. Negatives from one microscope were selected as guides and printed at convenient magnifications; then negatives from each of the other microscopes were projected to register with these prints. By deferring measurement to the print rather than comparing negatives, correspondence of magnification of the specimen in the three microscopes could be brought to within 2%.

Effect of Improved ThO2 Particle Dispersion in Nickel on High-Temperature Strength

1970 ◽  
Vol 28 ◽  
pp. 444-445
Author(s):  
E. R. Kimmel ◽  
H. L. Anthony ◽  
W. Scheithauer
Keyword(s):  
High Temperature ◽  
Metal Matrix ◽  
Oxide Particle ◽  
Oxide Phase ◽  
Dislocation Motion ◽  
Particle Dispersion ◽  
High Temperature Strength ◽  
Strengthening Effect ◽  
Oxide Particles ◽  
The Stability

The strengthening effect at high temperature produced by a dispersed oxide phase in a metal matrix is seemingly dependent on at least two major contributors: oxide particle size and spatial distribution, and stability of the worked microstructure. These two are strongly interrelated. The stability of the microstructure is produced by polygonization of the worked structure forming low angle cell boundaries which become anchored by the dispersed oxide particles. The effect of the particles on strength is therefore twofold, in that they stabilize the worked microstructure and also hinder dislocation motion during loading.

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