Martensitic Transformation, Structure and Magnetic Properties of Co-Ni-Ga Ferromagnetic Shape Memory Alloys

2007 ◽  
Vol 130 ◽  
pp. 141-146 ◽  
Author(s):  
B. Kostrubiec ◽  
Krystian Prusik ◽  
Ł. Madej ◽  
Henryk Morawiec
Keyword(s):  
Magnetic Properties ◽  
Martensitic Transformation ◽  
Structural Changes ◽  
Parent Phase ◽  
Martensite Phase ◽  
Ferromagnetic Shape Memory Alloys ◽  
Two Phase ◽  
Polycrystalline Alloys ◽  
Transformation Structure ◽  
Ferromagnetic Shape Memory

In the present paper the effect of heat treatment on microstructure, martensitic transformation temperatures and magnetic properties behavior of Co-Ni-Ga pollycrystal was discussed in detail. Microscopic observations revealed two types of two phase polycrystalline alloys: i) martensite with γ-precipitates and ii) parent phase with γ-precipitates. Making use of Xray and electron diffraction methods the crystal structure of martensite phase was identified as bct structure (with co/ao about 1.2). Annealing of Co-Ni-Ga alloy at 1223K/40 min causes a separation of martensitic and magnetic transformation and an increase of the Curie temperature by about 70K, after this annealing any significant structural changes in the parent (martensitic) and γ phase are not observed.

scholarly journals Tunable Martensitic Transformation and Magnetic Properties of Sm-Doped NiMnSn Ferromagnetic Shape Memory Alloys

Crystals ◽  
2021 ◽  
Vol 11 (9) ◽  
pp. 1115
Author(s):  
Najam ul Hassan ◽  
Mohsan Jelani ◽  
Ishfaq Ahmad Shah ◽  
Khalil Ur Rehman ◽  
Abdul Qayyum Khan ◽  
...  
Keyword(s):  
Magnetic Properties ◽  
Martensitic Transformation ◽  
Shape Memory Alloys ◽  
Shape Memory ◽  
Transformation Temperature ◽  
Room Temperature ◽  
Field Variation ◽  
Martensitic Transformation Temperature ◽  
Ferromagnetic Shape Memory Alloys ◽  
Ferromagnetic Shape Memory

NiMnSn ferromagnetic shape memory alloys exhibit martensitic transformation at low temperatures, restricting their applications. Therefore, this is a key factor in improving the martensitic transformation temperature, which is effectively carried out by proper element doping. In this research, we investigated the martensitic transformation and magnetic properties of Ni43Mn46-x SmxSn11 (x = 0, 1, 2, 3) alloys on the basis of structural and magnetic measurements. X-ray diffraction showed that the crystal structure transforms from the cubic L21 to the orthorhombic martensite and gamma (γ) phases. The reverse martensitic and martensitic transformations were indicated by exothermic and endothermic peaks in differential scanning calorimetry. The martensitic transformation temperature increased considerably with Sm doping and exceeded room temperature for Sm = 3 at. %. The Ni43Mn45SmSn11 alloy exhibited magnetostructural transformation, leading to a large magnetocaloric effect near room temperature. The existence of thermal hysteresis and the metamagnetic behavior of Ni43Mn45SmSn11 confirm the first-order magnetostructural transition. The magnetic entropy change reached 20 J·kg−1·K−1 at 266 K, and the refrigeration capacity reached ~162 J·Kg−1, for Ni43Mn45SmSn11 under a magnetic field variation of 0–5 T.

Structure and Phase Transformation in Ni-Co-Mn-In Ferromagnetic Shape Memory Alloys

2013 ◽  
Vol 203-204 ◽  
pp. 240-245
Author(s):  
Katarzyna Reclik ◽  
Krystian Prusik ◽  
Tomasz Goryczka ◽  
Marian Kubisztal ◽  
Danuta Stróż
Keyword(s):  
Phase Transformation ◽  
Martensitic Transformation ◽  
Room Temperature ◽  
Parent Phase ◽  
Indium Content ◽  
Gamma Phase ◽  
Ferromagnetic Shape Memory Alloys ◽  
Columnar Grains ◽  
One Step ◽  
Ferromagnetic Shape Memory

In the present study the series of the Ni46.2Co5.0Mn36.1In12.6, Ni48.7Co5.2Mn34.4In11.6 and Ni45.6Co4.8Mn36.4In13.2 alloys (at. %) were studied. The influence of the indium addition on structure and phase transitions was studied. All alloys were annealed at 900°C for 24 hours and then slowly cooled in the furnace. After annealing all of the studied alloys showed the macrostructure of radially oriented columnar grains, which lied in the direction perpendicular to the casting axis. For the alloy containing about 13 at. % of indium the monoclinic 14M modulated martensite was stated at room temperature. Apart from the modulated martensite in a1_133 alloy the gamma phase was also observed. For alloy with higher indium content the mixture of cubic L21 parent phase and cubic gamma phase was identified. All studied alloys showed one-step martensitic transformation.

TEM Studies on the Microstructure in Ferromagnetic Shape Memory Alloys

2008 ◽  
Vol 47-50 ◽  
pp. 515-518
Author(s):  
Y. Murakami ◽  
T. Yano ◽  
Daisuke Shindo
Keyword(s):  
Martensitic Transformation ◽  
Shape Memory Alloys ◽  
Shape Memory ◽  
Parent Phase ◽  
Magnetic Domain ◽  
High Temperature Phase ◽  
Phase Changes ◽  
Temperature Phase ◽  
Ferromagnetic Shape Memory Alloys ◽  
Ferromagnetic Shape Memory

The magnetic domain structures of the cubic parent phase (high-temperature phase) in ferromagnetic shape memory alloys (SMAs) have been studied by electron holography. In a Ni51Fe22Ga17 alloy, the magnetic flux distribution in the parent phase changes dramatically before the onset of martensitic transformation. In contrast, a Ni45Co5Mn36.7In13.3 alloy—a recently developed ferromagnetic SMA—does not show appreciable changes in the magnetic domain structure upon cooling. The anomaly observed in the Ni51Fe22Ga17 alloy appears to be due to lattice distortions, which become more pronounced as the temperature approaches the martensitic transformation start temperature, Ms.

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