Irradiation hardening in pure tungsten before and after recrystallization

Zhang, Zhexian; Chen, D.S.; Wang, Han; Kimura, Akihiko

doi:10.1016/j.fusengdes.2015.06.192

Cited by 43 publications

(21 citation statements)

References 22 publications

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“…Note that an adequate surface preparation, such as electro-polishing or vibratory polishing that produces a smooth surface free of any additional strain due to the sample preparation techniques themselves 78 , is critical for obtaining reliable indentation stress-strain curves from spherical nanoindentation on metallic samples 45 , 46 . Annealing of tungsten is also known to increase the irradiation-induced hardening as compared to the as-received samples, owing to a lesser density of grain boundaries (which can act as sinks for interstitials and vacancies) in the annealed sample 55 , 79 . The choice of tungsten was motivated in part due to (i) its potential use as a fusion reactor first wall material, (ii) the isotropy of its elastic response at the single crystal level (iii) which has been reported to be unchanged after ion-irradiation 56 .…”

Section: Methodsmentioning

confidence: 99%

Probing nanoscale damage gradients in ion-irradiated metals using spherical nanoindentation

Pathak

Kalidindi

Weaver

et al. 2017

Sci Rep

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We discuss and demonstrate the application of recently developed spherical nanoindentation stressstrain protocols in characterizing the mechanical behavior of tungsten polycrystalline samples with ionirradiated surfaces. It is demonstrated that a simple variation of the indenter size (radius) can provide valuable insights into heterogeneous characteristics of the radiation-induced-damage zone. We have also studied the effect of irradiation for the different grain orientations in the same sample.Materials with modified surfaces -either as a consequence of a graded microstructure or due to an intentional alteration of the surface such that its physical, chemical or biological characteristics are different from the bulk of the material -are of increasing interest for a variety of applications such as enhanced wear and corrosion resistance, superior thermal and biomedical properties, and higher fracture toughness 1,2 . In some cases such gradations at the surface may also be caused unintentionally as a consequence of the service life of the material, such as in wear applications 3 or irradiated materials which show varying degrees of radiation damage that change with depth, location of radiation source, etc.4 . Quantifying the resulting property gradations poses a significant challenge, especially when the changes occur over small (sub-micrometer) depths. In this communication, we present a novel indentation approach, which together with the corresponding local structure information obtained from electron back-scattered diffraction (EBSD), allows us to probe nanoscale surface modifications in solid materials and quantify the resulting changes in its mechanical response.The study of mechanical degradation in the surface layers of ion-irradiated materials is an example of one such outstanding challenge for which few practically viable solutions 4-7 exist. In materials undergoing irradiation in reactor or spacecraft applications, the resulting damage is often highly heterogeneous (with strong gradients normal to the surface) depending on component location as well as the nature of the irradiation source itself. In nuclear materials research, reactor conditions can be mimicked using ion beams where large amounts of radiation damage (several displacements per atom (dpa)) are imparted in relatively short time spans of hours or days that would require months or years to achieve in reactor conditions [8][9][10] . However, the volume of ion-irradiated material is limited by the beam energy to depths of fractions of a micron to several microns, making the investigation of bulk mechanical properties very difficult. A key challenge then becomes: "How can we study the mechanical response of materials with varying degrees of damage over scales of only a few hundreds of nanometers in such a way that the data can be related to bulk values?" The very small thickness of irradiated material, high level of damage heterogeneity, sensitivity to sample preparation techniques, and the time and effort needed for sample preparation and testi...

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Section: Methodsmentioning

confidence: 99%

Probing nanoscale damage gradients in ion-irradiated metals using spherical nanoindentation

Pathak

Kalidindi

Weaver

et al. 2017

Sci Rep

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“…Even though many studies have been performed on pure tungsten, e.g., material design, mechanical behavior, high heat flux properties [12] and irradiation behavior [13,14], there are only limited data available for recrystallization kinetics of rolled pure tungsten, e.g. [2,15].…”

Section: Introductionmentioning

confidence: 99%

Hardness loss and microstructure evolution of 90% hot-rolled pure tungsten at 1200–1350 °C

Wang

Zan

et al. 2017

Fusion Engineering and Design

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Tungsten is a promising plasma-facing material because of its low sputtering yield, high melting point and high thermal conductivity. The hardness loss and microstructure evolution of pure tungsten hot-rolled to 90% thickness reduction is investigated by isothermal annealing at temperature range of 1200 to 1350 °C. Changes in the mechanical properties caused by recovery and recrystallization during heat treatment are detected by Vickers hardness measurements. Additionally, the microstructural evolution is analyzed with light optical microscopy and X-ray diffraction. The results indicate that the hardness evolution can be divided into two stages: recovery and recrystallization. Recrystallization of W90 in the temperature range of 1200 to1350 °C is governed by the same activation energy as grain boundary diffusion. The average recrystallized grain size is larger for lower annealing temperatures.

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“…To simulate fusion environment for W, ion-irradiation is extensively in use [5][6][7][8][9][10] . A realistic estimation of the actual irradiation hardening behaviour by ion-irradiation experiments in W is essential in order to apply it as a plasma facing component in fusion power reactors.…”

Section: Introductionmentioning

confidence: 99%

Evaluation of Ion-Irradiation Hardening of Tungsten Single Crystals by Nanoindentation Technique Considering Material Pile-Up Effect

et al. 2017

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Ion-irradiation hardening of pure tungsten (W) single crystal was evaluated by nanoindentation (NI) technique considering material pileup effect. Pure W single crystals of (001) surface orientation were ion-irradiated with 6.4 MeV Fe 3+ to 0.1 dpa, 1 dpa or 2 dpa at 573 K. The irradiation hardening was evaluated by means of NI measurements with elastic-modulus-based correction (EMC) method [C. Heintze et al.: J. Nucl. Mater. 472 (2016) 196-205]. The effect of material pile-up in tungsten was so signi cant that the bulk equivalent hardness values by EMC method were about 70% and 85% of uncorrected results for irradiated and unirradiated W(001), respectively. The ion-irradiation hardening values by EMC based method were approximately 40%, 50% and 60% of uncorrected results for 0.1 dpa, 1 dpa and 2 dpa, respectively. The measured maximum pile-up height was higher for irradiated W(001) than for unirradiated W(001) at each indentation depth. An averaged pileup height that was associated with the actual area of contact of pile up obtained from EMC hardness showed different responses to ion-irradiation depending on the indentation depth.

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Irradiation hardening in pure tungsten before and after recrystallization

Cited by 43 publications

References 22 publications

Probing nanoscale damage gradients in ion-irradiated metals using spherical nanoindentation

Probing nanoscale damage gradients in ion-irradiated metals using spherical nanoindentation

Hardness loss and microstructure evolution of 90% hot-rolled pure tungsten at 1200–1350 °C

Evaluation of Ion-Irradiation Hardening of Tungsten Single Crystals by Nanoindentation Technique Considering Material Pile-Up Effect

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