Nano-crystalline formation during stress-induced amorphization at crack tips in TiNi

Tozawa, K.; Haishi, Y.; Matsukawa, Y.; Watanabe, Seiichi; Ohnuki, Somei; Takahashi, Hiroki

doi:10.1093/oxfordjournals.jmicro.a023726

Cited by 9 publications

(2 citation statements)

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“…This is the reason why there is no evidence or attempts in the literature to study the crystallization of non-polymeric materials when subjected to tensile stress. The literature contains evidence of stress-induced amorphization (c-a) in NiTi intermetallic compounds [8,9] as well as crystallization [10] and phase transition [11] in bulk metallic glasses. However, purely stress-induced crystallization (a-c) in amorphous metals is rarely reported in the literature.…”

Section: Introductionmentioning

confidence: 99%

Room temperature amorphous to nanocrystalline transformation in ultra-thin films under tensile stress: anin situTEM study

et al. 2010

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The amorphous to crystalline phase transformation process is typically known to take place at very high temperatures and facilitated by very high compressive stresses. In this study, we demonstrate crystallization of amorphous ultra-thin platinum films at room temperature under tensile stresses. Using a micro-electro-mechanical device, we applied up to 3% uniaxial tensile strain in 3-5 nm thick focused ion beam deposited platinum films supported by another 3-5 nm thick amorphous carbon film. The experiments were performed in situ inside a transmission electron microscope to acquire the bright field and selected area diffraction patterns. The platinum films were observed to crystallize irreversibly from an amorphous phase to face-centered cubic nanocrystals with average grain size of about 10 nm. Measurement of crystal spacing from electron diffraction patterns confirms large tensile residual stress in the platinum specimens. We propose that addition of the externally applied stress provides the activation energy needed to nucleate crystallization, while subsequent grain growth takes place through enhanced atomic and vacancy diffusion as an energetically favorable route towards stress relaxation at the nanoscale.

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Section: Introductionmentioning

confidence: 99%

Room temperature amorphous to nanocrystalline transformation in ultra-thin films under tensile stress: anin situTEM study

et al. 2010

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“…Crack propagation is followed by heat release at the tip. Supported by the tensile stress, this may give rise to a local glass transition [69][70][71][72][73][74][75][76] or a local melting [77][78][79][80].…”

Section: Experimental Observations Of Crack Tip Process Zonesmentioning

confidence: 99%

Field-theoretical description of the formation of a crack tip process zone

Boulbitch

Korzhenevskii

2016

Eur. Phys. J. B

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The crack tip process zone is regarded as a region where the solid physical properties are altered due to high stress. They are controlled by the solid degrees of freedom existing within the zone and vanishing outside, and can be divided into two classes: (1) zones always existing at the tip and (2) those emerging as soon as certain conditions are met. We focus on the zones of the second kind and argue that they can be described analogously to phase transitions taking place locally. We report both a numerical and an analytical solution for the process zone. We find that the zone can only exist within a limited domain of the dynamic phase diagram, at one side of the phase transition line. We describe this domain and establish its dependence on the crack velocity. We show the existence of a critical crack velocity above which the zone cannot exist.

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