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Heating of conductive materials by electric current is used in many technological processes. Application of electric pulses to metallic glasses induces their fast crystallization, which is an interesting and complex phenomenon. In this work, crystallization of the FeB amorphous alloy induced by pulses of electric current produced has been studied using X-ray diffraction and transmission electron microscopy. Ribbons of the alloy were directly subjected to single pulses of electric current 250 µs long formed by a capacitor discharge. As the value of $$\smallint I^{2} {\text{d}}t$$ was increased from 0.33 to 2.00 A s, different crystallization stages could be observed. The crystallization began through the formation of the nuclei of α-Fe. At high values of $$\smallint I^{2} {\text{d}}t$$ , α-Fe and tetragonal and orthorhombic FeB and FeB were detected in the crystallized ribbons with crystallites of about 50 nm. Thermal annealing of the ribbons at 600 °C for 2 min resulted in the formation of α-Fe and tetragonal FeB. It was concluded that pulses of electric current produced by a capacitor discharge induced transformation of the FeB amorphous phase into metastable crystalline products. [ABSTRACT FROM AUTHOR]

Ni- and Cu-free Zr-Al-Co-Ag bulk metallic glasses (BMGs) with diameters up to 20 mm were synthesized by copper mold casting. The effects of Ag alloying on the superior glass-forming ability (GFA) of Zr-Al-Co-Ag alloys were studied based on the localized atomic structure and crystallization behavior. High-energy synchrotron radiation x-ray diffraction result reveals that Ag addition in Zr-Al-Co system results in a more homogeneous local atomic structure, which could be an origin for the improved GFA of the Zr-Al-Co-Ag alloy. Crystallization products of the Zr-Al-Co-Ag glassy alloy are more complex than those of the Zr-Al-Co glassy alloy. The Zr-Al-Co-Ag BMGs free from highly toxic elements Ni and Cu exhibited a combination of superior GFA, high compressive fracture strength over 2000 MPa, low Young's modulus of 93 to 94 GPa, and good corrosion resistance in phosphate-buffered solution (PBS), inspiring their potential biomedical applications. [ABSTRACT FROM AUTHOR]

Despite significant research efforts, the deformation and failure mechanisms of metallic glasses remain not well understood. In the absence of periodic structure, these materials typically deform in highly localized, thin shear bands at ambient and low temperatures. This process usually leads to an abrupt fracture, hindering their wider use in structural applications. The dynamics and temperature effects on the formation and operation of those shear bands have been the focus of long-standing debate. Here, we use a new experimental approach based on localized boiling of liquid nitrogen by the heat generated in the shear bands to monitor the tensile plastic deformation of a bulk metallic glass submerged in a cryogenic bath. With the “nitrogen bubbles heat sensor”, we could capture the heat dissipation along the primary shear banding plane and follow the dynamics of the shear band operation. The observation of nitrogen boiling on the surface of the deforming metallic glass gives direct evidence of temperature increase in the shear bands, even at cryogenic temperatures. An acceleration in bubble nucleation towards the end of the apparent plastic deformation suggests a change from steady-state to runaway shear and premonitions the fracture, allowing us to resolve the sequence of deformation and failure events. [ABSTRACT FROM AUTHOR]

Using a cold graphite mold casting method, bulk AlNiY chill-zone alloys were prepared at hypereutectic compositions with Al content from 85 at.% to 94 at.%. It was found that ultra-hard surface layers with a thickness of about 200 µm and submicron grain size form when the melt can be undercooled without heterogeneous nucleation at the mold contact surface. This hard chill-zone forming in contact with the mold possesses Vickers microhardness Hv about 350-420 and is thus harder than fully amorphous Al alloys. In compression, ultimate strength more than 1.1 GPa and true strain more than 150% without failure were achieved simultaneously. The combination of high strength and good plasticity will be discussed in relation to the special structure of the chill-zone alloy. [ABSTRACT FROM AUTHOR]