Thermodynamic analysis of thermal measurements in thermoelastic martensitic transformations

Ortı́n, Jordi; Planes, Antoni

doi:10.1016/0001-6160(88)90291-x

Cited by 320 publications

(99 citation statements)

References 24 publications

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“…The entropy change is determined by a numeric integration of the thermograms. 23 The value obtained for the as-quenched system (1.27 Ϯ0.02 J/Kmol) is consistent with that reported in Ref. 24.…”

Section: Resultssupporting

confidence: 91%

“…Therefore, ⌬T represents a reasonable measure of the stored elastic energy during the forward transformation. 23 From this point of view, a decrease in ⌬T reflects a lower value of this stored elastic energy. We argue that the physical mechanism behind this effect is that the magnetic field around magnetic clusters breaks the degeneracy of the low-temperature martensitic phase thus favoring the nucleation of these variants with the magnetization easy axis in the direction of the field.…”

Section: Discussionmentioning

confidence: 99%

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Martensitic transition and magnetoresistance in a Cu-Al-Mn shape-memory alloy: Influence of ageing

et al. 2002

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We have studied the effect of ageing within the miscibility gap on the electric, magnetic, and thermodynamic properties of a nonstoichiometric Heusler Cu-Al-Mn shape-memory alloy, which undergoes a martensitic transition from a bcc-based structure (␤ phase͒ towards a close-packed structure (M phase͒. Negative magnetoresistance that shows an almost linear dependence on the square of magnetization with different slopes in the M and ␤ phases was observed. This magnetoresistive effect has been associated with the existence of Mn-rich clusters with the Cu 2 AlMn structure. The effect of an applied magnetic field on the martensitic transition has also been studied. The entropy change between the ␤ and M phases shows negligible dependence on the magnetic field, but it decreases significantly with annealing time within the miscibility gap. Such a decrease is due to the increasing amount of Cu 2 MnAl-rich domains that do not transform martensitically.

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Section: Resultssupporting

confidence: 91%

Section: Discussionmentioning

confidence: 99%

Martensitic transition and magnetoresistance in a Cu-Al-Mn shape-memory alloy: Influence of ageing

et al. 2002

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“…So, Q B19>B2 =2030 J/mol and Q CB,>B2 =1140 J/mol . According to Ortin and Planes [10], the difference between reverse and forward MT heats represents the amount of energy dissipated during the complete MT cycle Ed=Q M>A -Q A>M . For the second cycle of MT for ZrCu in general this dissipated energy will be E d " = 1345 -977 = 368 J/mol.…”

Section: Resultsmentioning

confidence: 99%

Peculiarities of the martensitic transformation in ZrCu intermetallic compound - potential high temperature SMA

2001

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Interaction of two martensitic phases during martensitic transformation (MT) in ZrCu intermetallic compound was studied by means of in situ high-temperature X-ray diffraction studies, internal friction and calorimetric measurements. Some regularities of the mutual formation and disappearance of two martensites on thermal cycling through the temperature interval of the MT were established. The mechanism of the MT in ZrCu intermetallic compounds is discussed.

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“…The entropy (AS) and the enthalpy (latent heat, L) changes at the martensitic transition have been obtained from calorimetric measurements after a proper correction of the calorimetric baseline as described in [9]. Within experimental uncertainties (evaluated to be less than 5%) no systematic differences between the AS values for forward (cooling) and reverse (heating) transitions have been detected.…”

Section: Martensitic Transitionmentioning

confidence: 99%

Influence of Composition and Thermal Treatments on the Martensitic Transition of Cu-Al-Mn Alloys

1997

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We have studied the martensitic transformation and the order-disorder transitions in two families of composition related Cu-Al-Mn crystals. X-ray diffraction and calorimetric measurements have been performed to characterize order-disorder transitions. The entropy change at the martensitic transition has been computed from calorimetric measurements. Results show that its magnitude depends only on the martensite structure which, in turn, depends on the electronic concentration e/a. We have obtained AS = 1.51 * 0.05 J mol-l K-l for a transition to a 2H phase and AS = 1.26 f 0.06 J mol-I K-I for a transition to a 18R structure. We discuss the possibility of a magnetic contribution to AS. Finally it is found that quenching has a marked influence on the martensitic transition temperature, but it does not affect the entropy change.

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Thermodynamic analysis of thermal measurements in thermoelastic martensitic transformations

Cited by 320 publications

References 24 publications

Martensitic transition and magnetoresistance in a Cu-Al-Mn shape-memory alloy: Influence of ageing

Martensitic transition and magnetoresistance in a Cu-Al-Mn shape-memory alloy: Influence of ageing

Peculiarities of the martensitic transformation in ZrCu intermetallic compound - potential high temperature SMA

Influence of Composition and Thermal Treatments on the Martensitic Transition of Cu-Al-Mn Alloys

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