Effect of Hf on the structure of Ni-Ti martensitic alloys

Potapov, Pavel; Shelyakov, A. V.; Gulyaev, A. A.; Svistunov, E.L.; Matveeva, N. M.; Hodgson, Darel E.

doi:10.1016/s0167-577x(97)00037-2

Cited by 93 publications

(59 citation statements)

References 4 publications

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“…We have also included on Figure 3 data on the system TiNiHf, which undergoes a cubic to monoclinic (B2 to B19') as in TiNi. The line is drawn using data of Matveeva et al [27] and Potapov et al [35] and was confirmed by our own measurements on this system. Alloys in the family TiNiHf, once considered promising candidates as high temperature shape memory alloys, show excessive hysteresis at concentrations of Hf that raise the transformation temperature significantly.…”

Section: Theoretical Methodssupporting

confidence: 81%

“…In such materials, all the eigenvalues of the transformation strain matrix are close to 1, and in materials with small volume change, λ 1 λ 2 λ 3 ∼ 1, λ 2 is particularly close to 1. In addition, the predicted asymptotic slopes of H vs. λ 2 at λ 2 = 1 tend to infinity as λ 1 , λ 3 → 1, because in that case a 2 n 2 → 0 (see (35)). Thus, the predicted graph of hysteresis H vs. λ 2 is sharper in the case of weak transformations, implying that one needs to approximate λ 2 = 1 with greater precision in order to achieve minimal hysteresis.…”

Section: Remarks and Comparisons With Other Ideas About Hysteresismentioning

confidence: 93%

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Energy barriers and hysteresis in martensitic phase transformations

2009

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Abstract. We report results from a systematic program of changing composition of alloys in the system TiNiX, X= Cu, Pt, Pd, Au, to pursue certain special lattice parameters that have been identified previously with low hysteresis. We achieve λ 2 = 1, where λ 2 is the middle eigenvalue of the transformation strain matrix, for alloys with X = Pt, Pd, Au. In all cases there is a sharp drop of the graph of hysteresis vs. composition at the composition where λ 2 = 1. When the size of the hysteresis is replotted vs. λ 2 we obtain an universal graph for these alloys, which also agrees with trends in an earlier combinatorial study of alloys in the system TiNiCu. Motivated by these experimental results, we present a new theory for the size of the hysteresis based on the growth from a small scale of fully developed austenite martensite needles. In this theory the energy of the transition layer plays a critical role. New methods for calculation the optimal layer are developed that rely on Γ-convergence arguments, the small parameter being |λ 2 − 1|. The limiting energy of the transition layer is found to be governed by a nonstandard linear elasticity problem. Overall, the results point to a simple systematic method of achieving low hysteresis and a high degree of reversibility in transforming materials.

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Section: Theoretical Methodssupporting

confidence: 81%

Section: Remarks and Comparisons With Other Ideas About Hysteresismentioning

confidence: 93%

Energy barriers and hysteresis in martensitic phase transformations

2009

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“…The presence of retained parent phase after the investigated parent ageing treatments suggests an incomplete transformation to martensite: retained parent phase is often found in literature 4,14) for melt spun ribbons of the same family obtained by similar preparation procedures.…”

Section: Ageing In Parent Phasementioning

confidence: 65%

“…The preparation procedure is described in papers. 4,5) All thermal treatments, except for the specimens to be examined by X Rays Diffraction (XRD), were performed in a Perkin-Elmer DSC7 Differential Scanning Calorimeter, under a high purity N 2 stream.…”

Section: Methodsmentioning

confidence: 99%

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Ageing in Parent Phase and Martensite Stabilization in a Ni50Ti30Hf20 Alloy

2003

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The effect of ageing in parent phase and martensite stabilization on melt spun Ni 50 Ti 30 Hf 20 ribbons were investigated by Differential Scanning Calorimetry and X Ray Diffraction. Thermal treatments in parent phase generally shift the martensitic transformation range as far as an equilibrium state is reached. The equilibrium state, here found for a thermal treatment at 450 C (723 K), was adopted as start state to investigate ageing in martensite (commonly indicated as martensite stabilization). Martensite stabilization involves diffusion processes with an activation energy in the order of 1.2 eV: results add a piece of evidence to the general principle of Symmetry-Conforming Short-Range Order advanced by Ren and Otsuka.

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