Microstructure evolution in CoNiGa shape memory alloys

Liu, Jian; Xie, Hongqiang; Huo, Yanqiu; Zheng, Hongxing; Li, Jianguo

doi:10.1016/j.jallcom.2005.10.056

Cited by 57 publications

(31 citation statements)

References 40 publications

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“…Despite their promise, these alloys have some limitations [3], the most important being their low ductility [5,6]. Recently, Co-Ni-Ga alloys [7][8][9][10][11][12][13][14][15][16][17][18] have emerged as an alternative to Ni 2 MnGa shape memory alloys (SMAs) [3] since they have excellent low-temperature conventional SM properties as well as strong potential as high-temperature SMAs due to their wide stress and temperature stability ranges [17,19], high melting temperatures, good oxidation resistance, and cyclic stability [11,20]. It has also been shown that Co-Ni-Ga alloys exhibit pseudoelastic behavior up to 450°C [12].…”

Section: Introductionmentioning

confidence: 99%

Investigation of the structural stability of Co2NiGa shape memory alloys via ab initio methods

et al. 2010

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Section: Introductionmentioning

confidence: 99%

Investigation of the structural stability of Co2NiGa shape memory alloys via ab initio methods

et al. 2010

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“…XRD of austenite phase corresponds to Ref. [6] and it crystallizes in body centered cubic (bcc) crystal structure, so according to [6] martensite phase should crystallize in face centered tetragonal (fct) structure at low temperature. The phase transformation exhibits a hysteresis, from which MT temperatures were obtained.…”

Section: Resultsmentioning

confidence: 99%

“…So far, many alloys with aforementioned properties have been discovered, for example alloys NiMnGa [2][3][4], FePd [5], CoNi(Al or Ga) [6][7][8][9], FeMnAlNi [10,11], Co2CrGaSi [12], or FSA are usually produced by arcmelting [6,9,11,12], by rapid solidification method, or by growing of single crystals [4,10] with additional annealing. However, melt spinning method can help to avoid * corresponding author; e-mail: jakub.mino@student.upjs.sk long-term annealing (or at least significantly reduce it) keeping good qu ality of highly textured polycrystalline ribbons [13].…”

Section: Introductionmentioning

confidence: 99%

Magnetic Characterization of Melt-Spun Co-Ni-Ga Ferromagnetic Superelastic Alloy

et al. 2017

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Ribbons of composition Co49Ni21Ga30 have been prepared by melt-spinning method. X-ray diffraction investigation revealed single phase with B2 structure at room temperature. However, analysis of magnetization dependence of temperature suggests phase transition in the range 150-250 K. Resistivity measurements revealed similar transition with shift to higher temperatures in the presence of magnetic field.

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“…Modulated martensites which are seen in Ni(Mn,Fe)Ga Heusler alloys, have not been observed in the CoNiGa system 10,11 . The L2 1 to L1 0 transformation can be described as a tetragonal distortion of the cubic austenitic phase.…”

Section: Introductionmentioning

confidence: 91%

Stability analysis of the martensitic phase transformation inCo2NiGaHeusler alloy

et al. 2015

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Phase competition and the subsequent phase selection are important characteristics of alloy systems exhibiting numerous states of distinct symmetry but comparable energy. The stoichiometric Co 2 NiGa Heusler alloy exhibits a martensitic transformation with concommitant reduction in symmetry from a austentic L2 1 phase (cubic) to a martensitic L1 0 phase (tetragonal). A structural search was carried out for this alloy and it showed the existence of a number of structures with monoclinic and orthorhombic symmetry with ground state energies comparable to and even less than that of the L1 0 structure, usually reported as the ground state at low temperatures. We describe these structures and focus in particular on the structural transition path from the L2 1 to tetragonal and orthorhombic structures for this material. Calculations were carried out to study the Bain (L2 1 − L1 0 ) and Burgers (L2 1 − hcp) transformations. The barrierless Burgers path yielded a stable martensitic phase with orthorhombic symmetry (O) with energy much lower-beyond the expected uncertainty of the calculation methods-than the known tetragonal L1 0 martensitic structure. This low energy structure (O) has yet to be observed experimentally and it is thus of scientific interest to discern the cause for the apparent discrepancy between experiments and calculations. It is postulated the the Co 2 NiGa Heusler system exhibits a classic case of the phase selection problem: although the unexpected O phase may be relatively more stable than the L1 0 phase, the energy barrier for the (L2 1 − O) transformation may be much higher than the barrier to the (L2 1 − L1 0 ) transformation. To validate this hypothesis, the stability of this structure was investigated by considering the contributions of elastic, vibrational effects, configurational disorder, magnetic disorder and atomic disorder. The calculations simulating the effect of magnetic disorder/ high temperature as well as the atomic disorder simulations showed that the transformation from L2 1 to L1 0 is favored over the Burgers path at high temperatures (large magnetic disorder). These conditions are prevalent upon cooling the material from high temperatures (the usual synthesis route), and this provides a plausible explanation why L1 0 and not the O phase is observed. Other ground states (not observed in experiments but predicted through calculations) are ruled out in terms of symmetry relations as well as through considerations of elastic barriers to their nucleation.

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Microstructure evolution in CoNiGa shape memory alloys

Cited by 57 publications

References 40 publications

Investigation of the structural stability of Co2NiGa shape memory alloys via ab initio methods

Investigation of the structural stability of Co2NiGa shape memory alloys via ab initio methods

Magnetic Characterization of Melt-Spun Co-Ni-Ga Ferromagnetic Superelastic Alloy

Stability analysis of the martensitic phase transformation inCo2NiGaHeusler alloy

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