The homogeneous plastic flow in bulk metallic glasses (BMGs) must be elucidated by an appropriate atomistic mechanism. It is proposed that a so-called concordant shifting model, based on rearrangements of five-atom subclusters, can describe the plastic strain behaviour of BMGs in a temperature range from room temperature to the supercooled liquid region. To confirm the effectiveness of the atomic concordant shifting model, a comparative investigation between the vacancy/atom model and the concordant shifting model is carried out based on the estimation of the strain rate deduced from two models. Our findings suggest that the atomic concordant shifting model rather than the vacancy/atom exchange model can well predict the large strain rate in the superplasticity of BMGs.

Due to the localization in space and the transience in time, investigations on the shear bands in metallic glasses are extremely difficult. The liquid-like layer frozen on fracture surfaces suggests a decreased viscosity in the shear band. Whether it is resulted from locally heating remains controversial. In this paper, the temperature rise in shear bands is profiled as a function of the duration of shear banding event, the distance from the shear band center and the thickness of shear band. The elastic energies released from the specimen and the testing machine are estimated regarding the serrations with different load drops in the compressive load–displacement curve of a Zr-based metallic glass. The duration of shear event and the released energy by serration are the two main factors determining the temperature rise in shear bands. It is found that both “cold” and “hot” shear bands are attainable. Then the sliding speed, the viscosity and the crystallization probability of shear band are studied. These results can help to better understand and describe the operation of shear band in a quantified and analytical way.

Al-Si-Fe-Cu-Mg alloy was prepared by spray deposition and was further processed by hot extrusion as well as T6 heat-treatment. The results indicate that the microstructure of the deposited alloy is composed of primary Si particles with average size of less than 5 μm, α-Al, Al2 CuMg, β-Al5 EeSi and δ-Al4FeSi2 (rectangular shape), and no eutectic silicon is found due to the special solidification behavior. The age hardening curves reveal two peaks. The uniform ultimate tensile strength (UTS) and the elongation of the peak-aged Al-Si-Fe-Cu-Mg alloy are 468. 3 MPa, 0.61% at 298 K and 267.4 MPa, 6.42% at 573 K, respectively. The fracture surfaces display brittle fracture morphology at 298 K, whereas it varies to mixture of brittle and ductile failure with increasing the temperature.

Cutting behavior exerts a considerable influence on the fabrication of bulk metallic glass (BMG) components. In this study, the influences of machining parameters (i.e., depth of cutting, feed rate, and spindle rate) on the turned surface of a Zr-based BMG after observing the 3D morphologies of this surface were characterized. The results showed that the influence of the spindle rate on the surface morphologies is more substantial as compared to the depth of cutting and the feed rate. Nanoscratch tests were conducted to further characterize the separation mechanism of the chips, which revealed that the chips are torn off the surface of a BMG because of inhomogeneous localized maximum shear stress.

Deviation values of specific heat difference \( \Updelta C_{\rm p},\) the Gibbs free energy difference \( \Updelta G , \) enthalpy difference \( \Updelta H , \) and entropy difference \( \Updelta S \) between the supercooled liquid and corresponding crystalline phase produced by the linear, hyperbolic, and Dubey’s expressions of \( \Updelta C_{\rm p}\) and the corresponding experimental values are determined for sixteen bulk metallic glasses (BMGs) from the glass transition temperature \( T_{\text{g}} \) to the melting temperature \( T_{\text{m}}. \) The calculated values produced by the hyperbolic expression for \(\Updelta C_{\rm p}\) most closely approximate experimental values, indicating that the hyperbolic \(\Updelta C_{\rm p}\) expression can be considered universally applicable, compared to linear and Dubey’s expressions for \( \Updelta C_{\rm p},\) which are accurate only within a limited range of conditions. For instance, Dubey’s \(\Updelta C_{\rm p}\) expression provides a good approximation of actual experimental values within certain conditions (i.e., \( \xi = \Updelta C_{\rm p}^{\rm g}/\Updelta C_{\rm p}^{\rm m}< 2 , \) where \(\Updelta C_{\rm p}^{\rm g}\) and \(\Updelta C_{\rm p}^{\rm m}\) represent the specific heat difference at temperatures \( T_{\text{g}} \) and \( T_{\text{m}} , \) respectively).

The quaternary Ti-Cu-Ni-Zr bulk metallic glasses are developed through proportionally mixing of the binary eutectic phases of Ti27Cu73, Ti76Ni24, Zr38Cu62 and Zr76Ni24. The novel Ti-Cu-based bulk metallic glasses with the critical diameter of 4 mm are successfully developed by the modification of the proportion of these eutectic units. The different glass forming ability (GFA) is discussed in a frame of thermodynamics. The GFA of these quaternary alloys correlate well with the reduced glass transition temperature (Trg), the γ value, the reduced ideal glass transition temperature (TK/Tm) (where TK is the ideal glass transition temperature) as well as the ratio between specific heat and entropy differences ΔCpm/ΔSm at the melting temperature (Tm).Highlights► A new Ti-based BMG with critical diameter of 4 mm is developed. ► GFA, δ and ΔCpm/ΔSm values are discussed based on the hole theory of liquid. ► Proportional modification of eutectic units cannot reduce GFA in the Ti-based alloy.

The structural behavior of binary Cu50Zr50 and ternary Cu50Zr45Ti5 bulk metallic glasses (BMGs) under applied stress was investigated by means of in-situ high energy X-ray synchrotron diffraction. The components of the strain tensors were determined from the shifts of the maxima of the atomic pair correlation functions (PDF) in real space. The anisotropic atomic reorientation in the first-nearest-neighbor shell versus stress suggests structural rearrangements in short-range order. Within the plastic deformation range the overall strain of the metallic glass is equal to the yield strain. After unloading, the atomic structure returns to the stress-free state, and the short-range order is identical to that of the undeformed state. Plastic deformation, however, leads to localized shear bands whose contribution to the volume averaged diffraction pattern is too weak to be detected. A concordant region evidenced by the anisotropic component is activated to counterbalance the stress change due to the atomic bond reorientation in the first-nearest-neighbor shell. The size of the concordant region is an important factor dominating the yield strength and the plastic strain ability of the BMGs.

•A plastic medium is introduced into the glassy phase to tune the shear avalanche.•The serrated flow in plastic regime of the CuZrTi alloy is statistically analyzed.•The geometric distribution of second phase dominates the shear avalanche.•The statistical distribution of shear-avalanche size follows power–law relationship.•Twinning in nanoscale can influence the shear-avalanche size in the CuZrTi alloy.Changes in intermittent shear avalanches during plastic deformation of a Cu50Zr45Ti5 (atomic percent) alloy in response to variant structures including fully glassy phase and/or nanocrystal/glass binary phase are investigated. Second crystalline phases are introduced into the glassy-phase matrix of a Cu50Zr45Ti5 metallic glass to interfere with the shear-avalanche process, which can release the shear–strain concentration, and then tune the critically-dynamic behavior of the shear avalanche. By combining microstructural observations of the nanocrystals with the statistical analysis of the corresponding deformation behavior, we determine the statistic distribution of shear-avalanche sizes during plastic deformation, and established its dependence on the geometric distribution of nanocrystals. The scaling behavior of the distribution of shear-avalanche sizes follows a power–law relation accompanied by an exponentially-decaying scaling function in the pure metallic glass, and the metallic glass containing the small nanocrystals, which can be described by the mean-field theory. The large shear-avalanche events are dominated by structural tuning-parameters, i.e., the resistance of shear banding, and the size and volume fraction of the second crystalline phase in metallic glasses.

•Al-based metallic glass degrade azo dye fast in alkaline and acidic solutions.•The nanoporosity on metallic glass surface contributes to the high reactivity.•In neutral solution, the precipitated Al(OH)3 particles accelerate decolorization.•Decrease of Y content in the metallic glass can increase the reactivity.The advanced efficiency of metallic glasses in degrading organic water pollutants has attracted wide interests. Yet the decolorization efficiency decreases in alkaline solutions which remains a challenge for their application. In this work, the performance of Al91-xNi9Yx (x = 0, 3, 6, 9 at.%) metallic ribbons in degrading azo dye in aqueous solutions at wide pH conditions is studied. It is surprising to find that the reaction activity of Al-based metallic glass in alkaline and acidic azo dye solution is about 1.5 and 189 times higher than that in neutral solutions, respectively. The low reaction activation energy and formation of nano-porosity on the surface of metallic glass are responsible for the high reactivity in alkaline and acidic solutions. The reaction activity can be further enhanced by modifying the alloy composition. These findings suggest that the Al-based metallic glasses hold promising potential in degrading azo dyes solutions, especially in alkaline and acidic environments.Al-based metallic glasses can degrade azo dyes fast in alkaline and acidic solutions. The positively charged [Alm(OH)n](3m-n)+ colloid particles precipitate at the second reaction stage in neutral solution and exhibit excellent adsorption ability to azo dye molecules, which can also decolorize the solution quickly and completely. The reaction activity can be further enhanced by modifying the alloy composition. Further investigation verifies that the lower reaction activation energy and formation of nano-porosity on the surface of metallic glass are responsible for the fast decolorization in alkaline and acidic solutions. These findings suggest that the Al-based metallic glasses hold promising potential in degrading azo dyes solutions, especially in alkaline and acidic environments.