Preparation and properties of fine grain β- CuAlNi strain- memory alloys

Mukunthan, Kannappar; Brown, L. C.

doi:10.1007/bf02647718

Cited by 55 publications

(30 citation statements)

References 17 publications

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“…They related their observation of a size effect in superelastic hysteresis to the increased pinning of the transformation front at free surfaces; the cross-over from volume to surface dominated physics was shown to take place in wires with diameters around, or just below, 100 µm. Another example of size dependent behavior in SMAs is that of polycrystalline SMAs, where several alloy families show a decrease in M s with decreasing grain size [60][61][62][63][64][65]. Interestingly, these effects also show little or no size dependence for large grains, but start to emerge for grain sizes below ∼100 µm.…”

Section: Obstacle Density and Morphologymentioning

confidence: 99%

Transition from many domain to single domain martensite morphology in small-scale shape memory alloys

Ueland

Schuh

2013

Acta Materialia

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Section: Obstacle Density and Morphologymentioning

confidence: 99%

Transition from many domain to single domain martensite morphology in small-scale shape memory alloys

Ueland

Schuh

2013

Acta Materialia

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“…For macroscopic polycrystalline samples with grain sizes larger than approximately 100 microns 5,6,7,8 the critical transformation temperature is a function of composition alone and relatively independent of microstructure and cooling rate. However, for nanoscale and nanostructured materials surfaces and interfaces play a large role and affect the phase transition temperature.…”

Section: Introductionmentioning

confidence: 99%

Size effects in NiTi from density functional theory calculations

Vishnu

Strachan

2012

Phys. Rev. B

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We use density functional theory to characterize how size affects the relative stability of thin NiTi slabs of different crystal structures and its implication on the martensitic phase transition that governs shape memory. We calculate the surface energies of B2' phase (austenite), B19 (orthorhombic), B19' (martensite) and a body centered orthorhombic phase (BCO), the theoretically-predicted ground state. We find that (110) B2 surfaces with in-plane atomic displacements stabilize the austenite phase with respect to B19' and BCO, thus slabs with such orientations are predicted to exhibit a decrease in martensite transition temperature with decreasing thickness. Our calculations predict a critical thickness of 2 nm, below which the transition would not occur. The opposite trend is observed in slabs with atomic displacements along the surface normal: the phase transformation temperature increases with decreasing size.

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“…The elastic modulus and the modulus of resilience were calculated as 11.8 ±2.2 GPa and 68.8 ±17.3 MJ/m³, respectively. Mukunthan and Brown 65 reported in a grain refined CuAlNi alloy similar fracture stress (1200 MPa) and strain (10%), achieved by sequential hot rolling operations. Their samples, however, were tested in tension 25,65 .…”

Section: Discussionmentioning

confidence: 59%

“…Mukunthan and Brown 65 reported in a grain refined CuAlNi alloy similar fracture stress (1200 MPa) and strain (10%), achieved by sequential hot rolling operations. Their samples, however, were tested in tension 25,65 . This exceptional mechanical behavior, earlier reported by Mukunthan and Brown 65 in tension and here found in compression, is not typical for alloys with SME, which usually presents a "pseudo-yield" plateau 18,30,38,50 and low values of maximum stress 6,22,41,49 .…”

Section: Discussionmentioning

confidence: 59%

“…Their samples, however, were tested in tension 25,65 . This exceptional mechanical behavior, earlier reported by Mukunthan and Brown 65 in tension and here found in compression, is not typical for alloys with SME, which usually presents a "pseudo-yield" plateau 18,30,38,50 and low values of maximum stress 6,22,41,49 . In other works 6,22,49,66 on CuAlNi polycrystalline SMAs, the ultimate strength was usually less than 500 MPa, especially due to the fragility of the grain boundaries, which makes them susceptible to intergranular stress cracking 6,25,41 .…”

Section: Discussionmentioning

confidence: 99%

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Martensitic Transformation Under Compression of a Plasma Processed Polycrystalline Shape Memory CuAlNi Alloy

et al. 2017

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Shape memory alloys (SMA) are attracting considerable attention owing to possible applications from biomedical to aerospace. In particular, CuAlNi alloys present significant advantages associated with low cost, easy processing and superior thermo-electric conductivity over other SMAs such as the NiTi alloys. Characterization of some properties and structural changes caused by martensitic transformation are still open to investigation. The present work evaluated these characteristics in an as-cast plasma processed shape memory Cu-14wt.%Al4wt.%Ni, which was compression tested until fracture. Experimental results showed that an as-cast ingot presents not only chemical and phase homogeneity, but also microstructures composed of grains with martensitic morphology. Martensites β' 1 and γ' 1 , as well as intermediary martensitic R and high temperature β 1 were identified by X-ray diffraction tests. It was found that the compressive deformation does not interfere in the phase composition and martensite morphology. However, compression changes the volumetric fractions and crystallographic orientation of the martensites. The mechanical behavior is characterized by an apparent elastic response until the fracture. The fractured surface exhibits brittle aspect like "river patterns" and evidence of intergranular rupture.

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Preparation and properties of fine grain β- CuAlNi strain- memory alloys

Cited by 55 publications

References 17 publications

Transition from many domain to single domain martensite morphology in small-scale shape memory alloys

Transition from many domain to single domain martensite morphology in small-scale shape memory alloys

Size effects in NiTi from density functional theory calculations

Martensitic Transformation Under Compression of a Plasma Processed Polycrystalline Shape Memory CuAlNi Alloy

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