Internal friction in cold-rolled metallic glasses Cu50Ti50 and Ni78Si8B14

Abstract

The influence of cold rolling on the low temperature (30 to 300 K) internal friction of metallic glasses Cu50Ti50 and Ni78Si8B14 is investigated. It is shown that cold rolling of both metallic glasses up to 2 to 6% results in the appearance of a high relaxation damping peak aroung 260 to 280 K. The internal friction background below the peak shows a strong amplitude dependence. In highly predeformed specimens (≈ 16%) the internal friction peak is absent. Electron irradiation (2 MeV, 1019 cm−2) leads to the suppression of the deformation‐induced internal friction peak. The results are interpreted in the framework of the dislocation models of plastic flow of metallic glasses.

Internal stresses induced by plastic shear deformation of Zr–(Cu,Ag)–Al bulk metallic glasses

“…It is interesting to compare the present results obtained on bulk glasses with earlier data [4,6] derived on ribbon MGs produced at melt quenching rates, which are larger by four orders of magnitude. Such a difference was shown to produce a twofold disparity in the starting free volume [11].…”

“…3). Earlier investigations [4][5][6], as mentioned above, revealed formation of huge internal stress upon room-temperature deformation (which is accompanied by shear banding) reaching 96% of the applied stress. This internal stress was found to be time independent during at least ≈ 1h [5].…”

“…The comparison is given in Fig. 3 in terms of the normalized shear internal stress as a function of the normalized temperature T/T c , where T c is the crystallization onset temperature (T g 's of glasses investigated in Refs [4,6] are not available). It is seen that the internal stresses occurring in bulk and ribbon glasses as well as their temperature dependences as are fairly similar.…”

“…Like in previous experiments [4][5][6], internal stresses were determined by measurements of stress relaxation upon stepwise unloading [3]. The measurements were performed using a special laboratory-made torsion testing micromachine.…”

“…The current information on this issue is limited, to our knowledge, to a few studies [4][5][6] performed in the nineties of the past century on ribbon Ni-Nb and Co-based glasses produced by conventional single roller melt spinning (production quenching rate R ∼ 10 6 K/s). It was found by means of stress relaxation measurements that roomtemperature tensile deformation leads to the formation of the internal stress σ i , which reaches 93% to 96% of the initially applied stress.…”