Dislocation Relaxation Peaks in High Purity Tungsten Single Crystals

Ziebart, U.; Schultz, H.

doi:10.1051/jphyscol:19839104

Cited by 7 publications

(4 citation statements)

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“…Figure 4(b and c) shows that the γ peak disappears in the second heating. This effect is probably associated with the annihilation and/ or bending of screw dislocations [27]. In addition, since the grain boundary peak in W occurs at around 1730 o C [29], it is safe to conclude that the grain boundary peak is not observed in this study.…”

Section: Fe-18wt%cr Steelmentioning

confidence: 48%

“…4(b and c). Similar peak was observed at 347-407ºC (the excitation frequency, 1-1.3 Hz) in high purity W single crystal after slight plastic deformations at 600 K and at 450 K [27,28]. This peak was defined as the γ peak observed in many bcc metals such as high purity Nb, Ta, Fe, and W. The γ relaxation was attributed to the kink-pair formation on screw dislocations in bCC metals [27].…”

Section: Fe-18wt%cr Steelmentioning

confidence: 62%

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Mechanical Spectroscopy Of Equal-Channel Angular Pressed Fe-Cr Alloys And Tungsten

Hao¹,

Tang²,

Jiang³

et al. 2015

Archives of Metallurgy and Materials

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Internal friction technique was used to investigate the microstructural stability of equal-channel angular pressed (ECAP) 9Cr1Mo steel (T91), Fe-18wt.%Cr alloy, and pure W. Several non-relaxation internal friction peaks are observed in three ECAP-strained specimens, which are related to the microstructural transition from a severely deformed state to a static recovery state of dislocations, and to recrystallized state. Along with the disappearance of the P1 peak, another relaxation internal friction peak P2 is observed during the second heating run only in Fe-18wt.%Cr alloy, and it does not disappear even during subsequent third heating run. This peak is not observed in T91 steel and W. The P2 peak is likely associated with a process of grain boundary (GB) sliding. Unlike T91, no abundant carbide precipitates distribute on GBs to pin GB and repulse GB sliding, thus, the P2 peak only occurs in Fe-18wt.%Cr alloy. It is concluded that high-temperature internal friction measurements are required to detect the grain boundary peak in pure W.

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Section: Fe-18wt%cr Steelmentioning

confidence: 48%

Section: Fe-18wt%cr Steelmentioning

confidence: 62%

Mechanical Spectroscopy Of Equal-Channel Angular Pressed Fe-Cr Alloys And Tungsten

Hao¹,

Tang²,

Jiang³

et al. 2015

Archives of Metallurgy and Materials

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“…In this second part, we summarize the outcomes of the work by Brunner [38], Brunner et al [36,37], Ziebart [44], and Ziebart et al [45] all on high-purity W single crystals [46]. At this point, we like to mention early fundamental work by Dorn et al [47], also addressing the Helmholtz energy of activation for kink-pair formation in bcc metals.…”

Section: Introductionmentioning

confidence: 96%

“…There is a lack of available data on the velocity of screw dislocations in W and related energies [21]. Available data about the plastic deformation of W refer to the process of kink-pair formation and were derived by conducting strain-relaxation tests and tensile test [36][37][38], as well as by the screening of the internal friction spectrum [44,45], cf. Refs.…”

Section: Introductionmentioning

confidence: 99%

The brittle-to-ductile transition in cold-rolled tungsten sheets: the rate-limiting mechanism of plasticity controlling the BDT in ultrafine-grained tungsten

et al. 2020

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Conventionally produced tungsten (W) sheets are brittle at room temperature. In contrast to that, severe deformation by cold rolling transforms W into a material exhibiting room-temperature ductility with a brittle-to-ductile transition (BDT) temperature far below room temperature. For such ultrafine-grained (UFG) and dislocation-rich materials, the mechanism controlling the BDT is still the subject of ongoing debates. In order to identify the mechanism controlling the BDT in room-temperature ductile W sheets with UFG microstructure, we conducted campaigns of fracture toughness tests accompanied by a thermodynamic analysis deducing Arrhenius BDT activation energies. Here, we show that plastic deformation induced by rolling reduces the BDT temperature and also the BDT activation energy. A comparison of BDT activation energies with the trend of Gibbs energy of kink-pair formation revealed a strong correlation between both quantities. This demonstrates that out of the three basic processes, nucleation, glide, and annihilation, crack tip plasticity in UFG W is still controlled by the glide of dislocations. The glide is dictated by the mobility of the screw segments and therefore by the underlying process of kink-pair formation. Reflecting this result, a change of the rate-limiting mechanism for plasticity of UFG W seems unlikely, even at deformation temperatures well below room temperature. As a result, kink-pair formation controls the BDT in W over a wide range of microstructural length scales, from single crystals and coarse-grained specimens down to UFG microstructures.

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