Effect of electron-irradiation on dislocation behaviour in nickel during deformation experiment in HVEM

Saka, Hiroyasu; Noda, K.; Matsumoto, K.; Imura, Toru

doi:10.1016/0036-9748(75)90340-3

Cited by 5 publications

(3 citation statements)

References 6 publications

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“…Irradiation effects appear more serious on dislocation behaviour during in situ deformation experiments. Saka et al (1975) found that dislocation motion during the in situ deformation of nickel was substantially different at 600, 800 and 1000 kV compared with 400 kV. Dose rates of between 2 x 102 A m-2 and 4 x 104 A m-2 above the threshold voltage were sufficient to nucleate secondary defects which impeded dislocation motion and produced a jerky flow by jogged dislocations.…”

Section: Efject Of Electron Irradiationmentioning

confidence: 95%

In situ experiments in the transmission electron microscope

Butler

1979

Rep. Prog. Phys.

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The possibility of using the objective region of a transmission electron microscope as a microlaboratory has long intrigued electron microscopists. They recognised that experiments conducted on specimens inside the microscope could provide direct evidence for the way in which a material responded to a change in state or environment. Such sophisticated experiments cannot be undertaken lightly. They involve the use of special stages designed to alter the state of a specimen in a controlled and measurable way, while at the same time permitting the continuous observation of the microstructure of the material. It is the purpose of this article to review the principles and practice of in situ experimentation in both conventional 100 kV microscopes and those operating at a higher accelerating potential, to provide a practical guide to the electron microscopist.The introductory sections deal with the important question of selecting the optimum image recording technique for the process being studied, and a discussion of the factors that can affect the validity of in situ observations. A description of the design and construction of in situ stages follows and serves to highlight the ingenuity of stage designers faced with the problem of providing services to the specimen in the restricted pole-piece gap region of a microscope without compromising microscope performance. Here an attempt has been made to describe selected stages which fulfil the basic principles of good stage design and which have been successfully employed to carry out in situ experiments. Discussion is confined to the four main types of stages fulfilling the functions of heating and cooling, deformation, environmental control and Lorentz imaging. The experimental application of in situ techniques forms the major part of this review. Emphasis has been placed on investigations producing results which could not have been obtained using other techniques, such as the direct observation of the movement, multiplication and interaction of dislocations, and the development of microstructural instabilities in crystalline solids subjected to electron irradiation. This section illustrates the unique nature of the information that can be obtained both at the qualitative and quantitative level by in situ experimentation.

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Section: Efject Of Electron Irradiationmentioning

confidence: 95%

In situ experiments in the transmission electron microscope

Butler

1979

Rep. Prog. Phys.

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“…Nickel is a model FCC metal and its hardening by irradiation has received significant attention by researchers in the past [8][9][10][11][12][13][14][15]. Investigations have established that irradiation of pure nickel by high energy neutrons causes the formation of SFT, voids, dislocation loops [8,9] and the interaction of these defects with dislocations results in hardening of the specimens [10].…”

Section: Introductionmentioning

confidence: 99%

“…They also found that the density of defects increased with increasing irradiation dose, which in turn increases the work hardening rate. Saka et al [13] studied the dislocation behaviour in electron irradiated nickel and noticed that irradiation causes jogs in dislocations and the formation of jogs locks dislocations [14], thus contributing to an increase in yield strength. Recently stress relaxation tests of proton irradiated nickel single crystals were performed in the temperature range 77-423 K by Yao et al [15].…”

Section: Introductionmentioning

confidence: 99%

Irradiation energy dependence of stress relaxation rate and activation volume in polycrystalline nickel

Ghauri¹,

Afzal²,

Raza³

2007

Phys. Scr.

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Stress relaxation in un-irradiated and electron beam irradiated polycrystalline nickel (99.99%) was studied at room temperature. The specimens were irradiated by high-energy electrons with energies in the range 8–18 MeV for 12 min at 300 K. The tensile tests of both un-irradiated and irradiated specimens were carried out at room temperature using a universal testing machine. During deformation, straining was frequently interrupted to observe stress relaxation at fixed loads. Measurements were made over the entire stress-strain curves up to fracture. The stress-relaxation was found to be logarithmic with time and its rate was found to decrease with an increase in the energy of incident electrons. The activation volume Vσ was observed to decrease with an increase in stress levels (σ0) both in un-irradiated and irradiated specimens, however Vσ values were higher in irradiated specimens than those of un-irradiated specimens. The intrinsic height of energy barrier (Uo) to the movement of dislocations increased with an increase in incident electron energy. The results are analysed in terms of a single barrier model of stress relaxation proposed by Feltham.

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