Composition-dependent elastic properties and electronic structures of off-stoichiometric TiNi from first-principles calculations

Lü, Jianmin; Hu, Qing‐Miao; Yang, Rui

doi:10.1016/j.actamat.2008.06.006

Cited by 26 publications

(18 citation statements)

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“…[25][26][27][28][29]). This correlation was confirmed for TiNi-based shape memory alloys and so on [30,31].…”

Section: Overviewsupporting

confidence: 71%

Composition dependent elastic modulus and phase stability of Ni2MnGa based ferromagnetic shape memory alloys

Luo

et al. 2011

Sci. China Technol. Sci.

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Ni 2 MnGa based ferromagnetic alloys are ideal candidates for applications such as actuators, magnetic refrigerators or magnetostrictive transducers due to their attractive properties such as magnetic field induced shape memory effect and large magnetocaloric effect. The properties of these alloys (e.g., the martensitic transformation temperature T M ) sensitively depend on the composition. Understanding the composition dependence of these properties so as to design the alloy as desired is one of the main research topics in this area. In recent years, we have investigated the composition dependent elastic modulus and phase stability of Ni 2 MnGa-based alloys by using a first-principles method, in hope of clarifying their connection to the properties of these alloys. In this article, we review the main results of our investigations. We show that the tetragonal shear modulus C' is a better predictor of the composition dependent T M than the number of valence electrons per atom (e/a) since the general T M~C ' correlation works for some of the alloys for which the T M~e /a correlation fails, although there exist several cases for which both the general T M~C ' and T M~e /a correlations break down. Employing the experimentally determined modulation function, the complex 5-layer modulated (5M) structure of the martensite of Ni 2 MnGa and the Al-doping effect on it are studied. We find that the shuffle and shear of the 5M structure are linearly coupled. The relative stability of the austenite and the martensites is examined by comparing their total energies. The non-modulated martensite   ′′′ with the tetragonality of the unit cell c/a>1 is shown to be globally stable whereas the 5M martensite with c/a<1 is metastable. The critical Al atomic fraction over which the martensitic transformation between the 5M martensite and austenite cannot occur is predicted to be 0.26, in reasonable agreement with experimental findings. Ni 2 MnGa, martensitic transformation, elastic modulus, phase stability, density functional theory Citation: Hu Q M, Luo H B, Li C M, et al. Composition dependent elastic modulus and phase stability of Ni 2 MnGa based ferromagnetic shape memory alloys.The ferromagnetic Ni 2 MnGa-based alloys have drawn much attention in recent years due to their attractive properties such as magnetic field induced shape memory effect and large magnetocaloric effect, resulting from the coupling between the magnetic and reversible martensitic transitions (e.g., refs. [1-4]). These properties make the alloys ideal candidates for applications such as actuators, magnetic refrigerators or magnetostrictive transducers, and so on. The shape memory effect results mainly from the reversible martensitic transformation (MT) between the high temperature austenite structure and the low temperature martensite. The austenite has cubic L2 1 structure as shown in Figure 1(a).

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“…[25][26][27][28][29]). This correlation was confirmed for TiNi-based shape memory alloys and so on [30,31].…”

Section: Overviewsupporting

confidence: 71%

Composition dependent elastic modulus and phase stability of Ni2MnGa based ferromagnetic shape memory alloys

Luo

et al. 2011

Sci. China Technol. Sci.

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“…Elastic constants and transformation paths for binary NiTi alloy have been calculated and are generally in agreement with the experiment and consistent between different computational approaches used [18,39,40]. Elastic constants calculated for offstoichiometric NiTi showed an increasing level of Zener elastic anisotropy in nickel-rich compositions, in contrast to a slight decrease in anisotropy when the titanium content increases [18].…”

Section: Introductionsupporting

confidence: 52%

“…Elastic constants calculated for offstoichiometric NiTi showed an increasing level of Zener elastic anisotropy in nickel-rich compositions, in contrast to a slight decrease in anisotropy when the titanium content increases [18]. Changes in the transformation temperatures in near-equiatomic nickel-titanium alloys, as documented in the literature [19,22,24], reflect a change in elastic constants of NiTi as a result of the off-stoichiometry.…”

Section: Introductionmentioning

confidence: 74%

“…A decrease in M s by % 100 K within concentration range 50-50.8 at.% Ni has been found whereas almost no change has been observed on the titanium-rich side for less than 50 at.% Ni [19,23,24]. The amount of strain accommodated by the martensitic phase can also change with the stoichiometry and composition of the alloy [18,7,25,26].…”

Section: Introductionmentioning

confidence: 74%

“…A stoichiometry change as low as 1% from near-equiatomic composition of NiTi has been found to drastically effect martensitic transformation (MT) temperatures such as those for martensite start and finish M s ; M f , and austenite start and finish A s ; A f [18][19][20][21]. Several authors reported this dramatic change in MT onset and finish temperatures with varying nickel content [19,22].…”

Section: Introductionmentioning

confidence: 98%

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