The origin of the deformation in metallic glasses is attributed to rearrangements of atoms in some structurally weak spots behaving as flow units, which are associated with free volumes. In the present study, Xe-ion beam is used to manipulate the free-volume fraction, and influence on the mechanical behavior of a Zr-based metallic glass. The irradiation at low dosages can change the structure by increasing the free volume, and by homogenising the distribution of free volume. The increase in the free-volume fraction is equivalent to the increase in the deformation temperature, thus resulting in the decrease in the yield strength. The analysis of stochastic strain burst size in the metallic glass irradiated at different dosages indicates that the strain burst depends on the yield strength and homogeneity of the glassy phase. The results of this study highlight the fact that the quantitative manipulation of the homogeneity and the amount of free volumes can be achieved through low-dose ion irradiation, which can modify the mechanical behavior of metallic glasses.

Articles you may be interested in Microstructure and nonlinear signatures of yielding in a heterogeneous colloidal gel under large amplitude oscillatory shear Strain rate effects in beryllium under shock compression AIP Conf. Abstract. Attractive colloidal particles are trapped in metastable states such as colloidal gels at high attraction strengths and attractive glasses and high volume fractions. Under shear such states flow via a two step yielding process that relates to bond and cluster or cage breaking. We discuss the way the structural properties and related stress response are affected by the shear rate. At low rates colloidal gels yield during start-up shear essentially in a single step, exhibiting a single stress overshoot due to creation of compact flowing clusters. With increasing shear rate a second stress overshoot, linked with further cluster breaking up to individual particles, is becoming more pronounced. We further present the age dependence of the two step yielding and wall slip effects often taking place during rheological experiments of colloidal gels. The latter is related both with the shear rate dependent gel structure as well as the time evolution of the near wall structure.

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The purification process of commercial organoclays and the beneficial effect of the impurities removal on the mechanical properties of the EVA exfoliated and intercalated nanocomposites are described in this paper. Mechanical properties such as Young modulus are improved, without any change in morphology in the exfoliated nanocomposites and an improvement of intercalation degree in the intercalated nanocomposite as demonstrated by rheological test is observed.

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Cooling shrinkage can increase the atomic packing density of metallic glasses, which can influence their elastic and plastic behaviour. In the present study, the compressive deformation behaviour of a Zr-based metallic glass at temperatures well below the glassy transition temperature, say 123 K to room temperature, is experimentally revealed. The elastic modulus and the shear modulus at different temperatures are measured to elucidate the yield strength changes with temperature according to the model of shear transformation zones. In the plastic regime, based on the SEM observation and the digital scattering correlation method, an enhanced interaction between the elastic shear strain fields initiated by neighbouring shear bands is discussed, which explains the amplitude of serration events decreasing with the temperature decreasing. V C 2013 AIP Publishing LLC.

The plasticity of metallic glasses depends largely on the atomic-scale structure. However, the details of the atomic-scale structure, which are responsible for their properties, remain to be clarified. In this study, in-situ high-energy synchrotron X-ray diffraction and strain-rate jump compression tests at different cryogenic temperatures were carried out. We show that the activation volume of flow units linearly depends on temperature in the non-serrated flow regime. A plausible atomic deformation mechanism is proposed, considering that the activated flow units mediating the plastic flow originate from the medium-range order and transit to the short-range order with decreasing temperature. IMPACT STATEMENTAn atomic deformation mechanism in metallic glasses is proposed. Activated flow units mediating the plastic flow originate from the medium-range order and transit to the short-range order with decreasing temperature.