Changes in stacking fault sequences during the martensitic phase transformation in CuZnAl shape memory alloys

Stoiber, J.; Gotthardt, R.

doi:10.1016/0921-5093(93)90709-n

Cited by 12 publications

(7 citation statements)

References 8 publications

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“…It results from the collective activation of dislocations, which form the variant interfaces, by the measurement strain during the IF experiments. In another study, 9,10 it was shown that the displacement of martensite/martensite interfaces together with the motion of PDs observed in situ in the TEM could be related to the application of an a t50 s; b t52 s; c t516 s; d t528 s 5 Transmission electron microscopy weak beam micrographs of moving PD with gliding planes nearly perpendicular to observation direction: a-c dislocations appear as growing loops (indicated by the black arrow) between pinning points, d loop depinns at one point and continues to move stepwise as stress increases and e schematic representation external stress and the creation of a local elastic (internal) stress.…”

Section: Discussionmentioning

confidence: 95%

“…The martensitic transformation is at the origin of properties such as shape memory effect, superelasticity and high damping capacity (internal friction, IF). The most known shape memory alloys are NiTi binary and ternary alloys with additions of Cu, Fe, 6 Hf, 7 or Pd, 8 ternary Cu based alloys like CuZnAl, 9,10 or CuNiAl and less common noble metals shape memory alloys such as AuCd or AgCd. 1 NiTi alloys are among the most interesting ones for applications.…”

Section: Introductionmentioning

confidence: 99%

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Relaxation mechanisms in martensitic NiTi(Cu): Internal friction measurements correlated to in situ TEM straining

Parlinska-Wojtan¹,

Schäublin²,

Gotthardt³

2008

Materials Science and Technology

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The microstructural origin of the internal friction response in B19' martensitic NiTiCu polycrystals is investigated by in situ TEM straining experiments. Internal friction measurements showed that the transient contribution Q 21Tr , determined as a function of temperature in martensitic state, vanishes when the heating or cooling is stopped. In situ TEM experiments evidence defects moving across the martensitic variants along the microtwin boundaries. They are identified as partial dislocations (PDs). They move under applied stress as well as under temperature gradients. In the present study a correlation between their movement and the changes of Q 21Tr is proposed. The Q 21 Tr is found to be sensitive to the density of PDs depinned from the martensite variant boundaries. Their movement appears to be a reversible process, as when stress is released the PDs return into the variant interface and consequently Q 21 Tr value drops.

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Section: Discussionmentioning

confidence: 95%

Section: Introductionmentioning

confidence: 99%

Relaxation mechanisms in martensitic NiTi(Cu): Internal friction measurements correlated to in situ TEM straining

Parlinska-Wojtan¹,

Schäublin²,

Gotthardt³

2008

Materials Science and Technology

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“…This model takes into account the interaction between the martensitic stress-free transformation strains and the stress field created by the dislocation arrays. 49,50 Interactions between twin boundaries and stacking faults 51 and changes of stacking sequences during the martensitic transformation in Cu−Zn−Al SMAs are reported in ref 52 and the coexistence of twins and stacking faults in ref 53.…”

mentioning

confidence: 99%

“…A previous microscopic model explains the inhibition of the martensitic transformation in bulk Cu–Al–Ni, related to the localized interaction between a dislocation array and the twinned 2 H structure. This model takes into account the interaction between the martensitic stress-free transformation strains and the stress field created by the dislocation arrays. , Interactions between twin boundaries and stacking faults and changes of stacking sequences during the martensitic transformation in Cu–Zn–Al SMAs are reported in ref and the coexistence of twins and stacking faults in ref .…”

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confidence: 99%

Breakdown of Shape Memory Effect in Bent Cu–Al–Ni Nanopillars: When Twin Boundaries Become Stacking Faults

et al. 2015

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Bent Cu–Al–Ni nanopillars (diameters 90–750 nm) show a shape memory effect, SME, for diameters D > 300 nm. The SME and the associated twinning are located in a small deformed section of the nanopillar. Thick nanopillars (D > 300 nm) transform to austenite under heating, including the deformed region. Thin nanopillars (D < 130 nm) do not twin but generate highly disordered sequences of stacking faults in the deformed region. No SME occurs and heating converts only the undeformed regions into austenite. The defect-rich, deformed region remains in the martensite phase even after prolonged heating in the stability field of austenite. A complex mixture of twins and stacking faults was found for diameters 130 nm < D < 300 nm. The size effect of the SME in Cu–Al–Ni nanopillars consists of an approximately linear reduction of the SME between 300 and 130 nm when the SME completely vanishes for smaller diameters.

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“…The analysis, however, was made ex-situ on stress-induced martensites in the unstressed state. In order to obtain a closer insight into the dynamically evolving microstructures, in-situ TEM straining experiments seem to be a very suitable technique [12][13][14][15][16].…”

Section: Introductionmentioning

confidence: 99%

In-situTEM study of stress-induced transformations in CuAlNi

Zárubová

Gemperlová

Gemperle

et al. 2009

ESOMAT 2009 - 8th European Symposium on Martensitic Transformations

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Abstract. Stress-induced martensitic transformations and twinning processes were studied in thin foils of CuAlNi single crystals strained in-situ in a transmission electron microscope. A detailed structure analysis comprised identification of phases existing under stress and determination of their mutual crystallographic orientation. Three transformation processes were detected: i) transformation of austenite into 2H martensite at low stress levels; ii) twinning/detwinning processes in 2H martensite, and iii) transformation between austenite and 18R martensite at higher stress levels. Nucleation and growth of martensite plates were followed, and morphology of the austenite/martensite habit planes was examined. Existence of planar interfaces between a single variant of 2H martensite and austenite on microscopic level was proved.

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Changes in stacking fault sequences during the martensitic phase transformation in CuZnAl shape memory alloys

Cited by 12 publications

References 8 publications

Relaxation mechanisms in martensitic NiTi(Cu): Internal friction measurements correlated to in situ TEM straining

Relaxation mechanisms in martensitic NiTi(Cu): Internal friction measurements correlated to in situ TEM straining

Breakdown of Shape Memory Effect in Bent Cu–Al–Ni Nanopillars: When Twin Boundaries Become Stacking Faults

In-situTEM study of stress-induced transformations in CuAlNi

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