Orientation dependence of slip in niobium single crystals at 4.2 and 77 K

Multiscale modeling of plastic deformation of molybdenum and tungsten: I. Atomistic studies of the core structure and glide of 1/2〈111〉 screw dislocations at 0K

“…The result of the present atomistic studies that is common to both molybdenum and tungsten and to all modes of loading is that {110} planes are the glide planes of 1/2〈111〉 screw dislocations at 0 K. This is in agreement with experimental observations of slip planes in molybdenum samples deformed at cryogenic temperatures, whether loaded in pure shear [14,96,97] or tension/compression [17,[98][99][100][101][102]. Moreover, {110} planes were found to be the principal slip planes in other BCC metals.…”

“…The occurrence of the slip on the (011) and (110) planes is reminiscent of the anomalous slip that takes place on the slip systems for which the resolved shear stress is substantially lower than that for the most highly stressed {110} 〈111〉 system. Such slip was observed in niobium [10,11,102,[104][105][106][107], tantalum [108], vanadium [109,110] and molybdenum [100,111,112]. Indeed, the anomalous slip observed by Jeffcoat et al [111] in Mo-5at%Nb and Mo-5at%Re deformed in compression at 77 K can be adequately explained on the basis of our results.…”

Anomalous Slip - A Feature of High-Purity Body-Centred Cubic Metals

“…The present explanation accounts for the observations at least qualitatively if the work on thin samples [46,47] is disregarded as not pertaining to bulk anomalous slip. A more quantitative comparison experiment-theory would require considerably more systematic and extensive data than available so far.…”

“…In the first case a foil with A in the middle of the standard triangle with a thickness of 200 mm had been deformed to 9.7% in tension at 10 K [46]. In the second case an Nb crystal with the residual resistivity ratio RRR ¼ 200, a square cross section of 400 mm side length, and c ¼ þ10 was deformed at 4.2 K [47]. We presume that in both cases surface effects as studied by Veselý [22] and others (e.g., [23]) were dominant.…”

Multiscale modeling of plastic deformation of molybdenum and tungsten. III. Effects of temperature and plastic strain rate

“…The tension-compression asymmetry predicted for W is even larger than for Mo. Furthermore, in compression the system (110)[1 1 1] dominates over the most highly stressed system (101)[1 1 1] system at temperatures below 150 K. This is reminiscent of the anomalous slip that occurs on the slip systems for which the resolved shear stress is significantly lower than for the most highly stressed {110} 〈111〉 system and that was observed in a number of BCC transition metals at low temperatures (see, for example [54][55][56][57][58][59][60]). Unfortunately, to our knowledge, no experimental studies of W that could be compared with these predictions have been made.…”