On the anisotropy of martensitic transformations in Cu-based alloys

Novák, V.; Šittner, Petr; Vokoun, D.; Zárubová, N.

doi:10.1016/s0921-5093(99)00355-x

Cited by 54 publications

(31 citation statements)

References 9 publications

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“…Particularly for the presently studied crystal, the tensile stress induced MT's are reported in [10]. Less known is the behavior in compression [5], where the /3;->/3'i closely followed by Pi->P'i->y'i transformation is responsible for the stress-strain curves of the character demonstrated in figure 2b. At the onset of the straining, only the pi' martensite is induced, which is clearly evidenced by the narrow hysteresis partial stress-strain curves.…”

Section: Experimental Evaluation Of Stress-temperature Transformationmentioning

confidence: 84%

“…The stress-strain behaviour described in Figures 2 and 3 [4,5,6,9] especially concerning the shape of the pseudoelastic loops, transformation strains and temperature dependence of transformation stresses. What is different is that the test temperatures to study the same phenomena are 200K higher, and that the thermally induced martensite phase is not the yt' but the pi' phase.…”

Section: Experimental Evaluation Of Stress-temperature Transformationmentioning

confidence: 99%

“…There is thus no wonder that the history dependent phenomena are quite complex and can be easily confused with martensite stabilization especially when studied on polycrystalline alloys. Recently, we have investigated systematically the effects of anisotropy [5] and tension/compression sense of load [6] on the martensitic transformations in oriented CuAINi alloy single crystals with higher Al content (M S~2 00K) which transform to the y'i martensite phase upon stress free cooling. The results were presented in a form of stress-temperature non-equilibrium, CT-T, diagrams which provide complete sets of information on transformation conditions and history dependent phenomena exhibited by the given crystals.…”

Section: Introductionmentioning

confidence: 99%

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Martensitic transformations of Cu-Al-Ni single crystals in tension/compression

2001

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Abstract. Cu-AI-Ni alloys, similarly as other Cu-base shape memory alloys, transform into more martensitic structures c^' (6R), Pi' (18R) and y x ' (2H), depending on the temperature, stress, load axis orientation, sense of loading and composition. The transformation stress-temperature conditions at which individual transitions take place are beneficially represented in so called non-equilibrium stress-temperature phase diagrams. On the basis of the 363K) and comparison with our previous results obtained on alloys with higher Al content (T 0 <263K).

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Section: Experimental Evaluation Of Stress-temperature Transformationmentioning

confidence: 84%

Section: Experimental Evaluation Of Stress-temperature Transformationmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Martensitic transformations of Cu-Al-Ni single crystals in tension/compression

2001

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“…The values of Dm = dsm/dGG (Table 1) determined from the linear elastic range correspond approximately but not exactly (due to the load partition in the polycrystal) with the Em values calculated by Eq. (2). Note that the individual ^/-responses (Table 1, Figs 4,5) differ in: \)D h ki, U)£m pU -lattice strain at which the deviation from linearity on the Em-0G curve appears, iii) type of the Em -<?G non-linearity following the start of the SIMT, iv) Shu hysteresis width, v) parameter I p ,hki/Io,hki characterizing the maximal decrease of the normalized integral intensity due to the SIMT, and vi) Em es residual strain left behind the first tensile load cycle.…”

Section: Constant Temperature the Transformation Stress D'm -L/d'm Cmentioning

confidence: 99%

“…Since SMAs are often elastically anisotropic and the SIMT is also a strongly anisotropic process [1,2], it might be in fact very difficult for some SMA polycrystals to sustain larger recoverable strains in polycrystalline state [3], even if their theoretical crystallographic transformation strains are of the order of 10%. We are interested in this paper in the stress redistribution among grains of SMA polycrystal undergoing SIMT in tensile pseudoelastic cycles.…”

Section: Introductionmentioning

confidence: 99%

Stress induced martensitic transformation in CuAlZnMn polycrystals investigated by in situ neutron diffraction

et al. 2001

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Abstract. The results of in-situ neutron diffraction investigation of stress induced martensitic transformation in CuAIZnMn shape memory alloy polycrystal are reported. Time-of-flight diffraction spectra were measured during temporary stopovers along two successive tensile pseudoelastic cycles. The integral intensities, positions and widths of multiple individual austenite and martensite ^-reflections from the recorded spectra were evaluated by single peak fits. The evaluated peak profile parameters were used to calculate the lattice strains in the austenite phase and volume fractions of the austenite phase evolving during the pseudoelastic cycles. The obtained /nW-lattice plane responses were related to the elastic anisotropy of the cubic austenite phase and to the transformation anisotropy of the pi->P*i martensitic transformation in CuAIZnMn using a selfconsistent crystallographic model of SMA polycrystals. The mechanism of the load partition among polycrytal grains has been discussed and claimed to be a major obstacle for the stress driven transformability of the polycrystalline Cu-based SMAs It has been found that significant redistribution of stress and large intergranular stresses but no strong transformation induced texture should be expected in Cu based SMA polycrystals transforming pseudoelastically in tension. 1.INTRODUCTIONWhen shape memory alloy /SMA/ polycrystal undergoes stress induced martensitic transformation /SIMT/, the compatibility of strains and continuity of stress across grain boundaries must be fulfilled. Since SMAs are often elastically anisotropic and the SIMT is also a strongly anisotropic process [1,2], it might be in fact very difficult for some SMA polycrystals to sustain larger recoverable strains in polycrystalline state [3], even if their theoretical crystallographic transformation strains are of the order of 10%. We are interested in this paper in the stress redistribution among grains of SMA polycrystal undergoing SIMT in tensile pseudoelastic cycles. Recent developments of in-situ neutron diffraction technique of strain measurement have allowed to study this experimentally as we will demonstrate in this paper.Due to the large penetration depths of thermal neutrons, neutron diffraction is a suitable tool for nondestructive in-situ measurement of elastic strains (and evaluation of stresses) within the bulk of large polycrystal specimens. Diffraction strain measurements rely on the precise measurement of the duaspacing of particularly oriented crystal planes. Knowing the stress free lattice spacing do,hki,, the lattice strain E h u can be calculated according to equation (1).(1)The diffraction evaluated strains are: i) elastic strains only, ii) determined selectively only from those grains of the specimen which are suitably oriented, iii) averaged strain values over those grains, and iv) generally only one component of the elastic strain tensor can be evaluated from a diffraction experiment with a single specimen orientation with respect to the scattering vector. The lattice str...

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Corrosion behavior of two Cu‐based shape memory alloys in NaCl solution: An electrochemical study

Spotorno,

Fracchia,

Krancher

et al. 2024

Materials & Corrosion

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The corrosion behavior of two different Cu–Al–Mn–Ni alloys, pseudoelastic and pseudoplastic, was studied in a 0.6 M sodium chloride aqueous solution by monitoring the open circuit potential for 100 h and characterizing the resulting corrosion products. Electrochemical impedance spectroscopy analysis detected three processes related to the electrochemical double layer, a passive film and a diffusive contribution associated with the dissolution/precipitation of corrosion products. Potentiodynamic scans revealed a cathodically controlled corrosion mechanism and the presence of active–passive behavior at anodic potentials for both alloys studied. Polarization of the samples at selected potentials in the anodic branch allowed the investigation of the reactions involved, highlighting an improved corrosion resistance of the pseudoelastic alloy. The corrosion rates of the pseudoelastic and pseudoplastic alloys, after 100 h of immersion, were determined to be 0.007 and 0.011 mmpy, respectively. The post‐experiment characterization was carried out by means of scanning electron microscopy, micro‐Raman spectroscopy and X‐ray diffraction, supporting the electrochemical results.

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On the anisotropy of martensitic transformations in Cu-based alloys

Cited by 54 publications

References 9 publications

Martensitic transformations of Cu-Al-Ni single crystals in tension/compression

Martensitic transformations of Cu-Al-Ni single crystals in tension/compression

Stress induced martensitic transformation in CuAlZnMn polycrystals investigated by in situ neutron diffraction

Corrosion behavior of two Cu‐based shape memory alloys in NaCl solution: An electrochemical study

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