Unveiling the Local Atomic Arrangements in the Shear Band Regions of Metallic Glass

The prospective applications of metallic glasses are limited by their lack of ductility, attributed to shear banding inducing catastrophic failure. A concise depiction of the local atomic arrangement (local atomic packing and chemical short‐range order), induced by shear banding, is quintessential to understand the deformation mechanism, however still not clear. An explicit view of the complex interplay of local atomic structure and chemical environment is presented by mapping the atomic arrangements in shear bands (SBs) and in their vicinity in a deformed Vitreloy 105 metallic glass, using the scanning electron diffraction pair distribution function and atom probe tomography. The results experimentally prove that plastic deformation causes a reduction of geometrically favored polyhedral motifs. Localized motifs variations and antisymmetric (bond and chemical) segregation extend for several hundred nanometers from the SB, forming the shear band affected zones. Moreover, the variations within the SB are found both perpendicular and parallel to the SB plane, also observable in the oxidation activity. The knowledge of the structural–chemical changes provides a deeper understanding of the plastic deformation of metallic glasses especially for their functional applications and future improvements

Nanomaterials by severe plastic deformation: review of historical developments and recent advances

International audienceSevere plastic deformation (SPD) is effective in producing bulk ultrafine-grained and nanostructured materials with large densities of lattice defects. This field, also known as NanoSPD, experienced a significant progress within the past two decades. Beside classic SPD methods such as high-pressure torsion, equal-channel angular pressing, accumulative roll-bonding, twist extrusion, and multi-directional forging, various continuous techniques were introduced to produce upscaled samples. Moreover, numerous alloys, glasses, semiconductors, ceramics, polymers, and their composites were processed. The SPD methods were used to synthesize new materials or to stabilize metastable phases with advanced mechanical and functional properties. High strength combined with high ductility, low/room-temperature superplasticity, creep resistance, hydrogen storage, photocatalytic hydrogen production, photocatalytic CO2 conversion, superconductivity, thermoelectric performance, radiation resistance, corrosion resistance, and biocompatibility are some highlighted properties of SPD-processed materials. This article reviews recent advances in the NanoSPD field and provides a brief history regarding its progress from the ancient times to modernity

Enhanced Erosion Resistance of an Ultrafine-Grained Ti Alloy with a PVD Coating

This paper presents the results of a comprehensive study of the erosive wear resistance, strength, and adhesive characteristics of the high-temperature structural titanium alloy Ti-5.7Al-3.8Mo-1.2Zr-1.3Sn (the Russian grade VT8M-1) with coarse-grained and ultrafine-grained (UFG) structures and a protective erosion-resistant TiVN coating produced by physical vapor deposition (PVD), deposited on the alloy surface. A microscopic analysis of the areas subjected to the action of abrasive particles was performed, and different characters of erosive wear were revealed depending on the structural state of the alloy. The obtained results convincingly demonstrate that by means of refining the grain structure of alloys and depositing a protective ion-plasma TiVN coating on the alloy surface, it is possible to significantly increase the erosion resistance of materials operating under high loads and in aggressive environments

Enhanced Erosion Resistance of an Ultrafine-Grained Ti Alloy with a PVD Coating

This paper presents the results of a comprehensive study of the erosive wear resistance, strength, and adhesive characteristics of the high-temperature structural titanium alloy Ti-5.7Al-3.8Mo-1.2Zr-1.3Sn (the Russian grade VT8M-1) with coarse-grained and ultrafine-grained (UFG) structures and a protective erosion-resistant TiVN coating produced by physical vapor deposition (PVD), deposited on the alloy surface. A microscopic analysis of the areas subjected to the action of abrasive particles was performed, and different characters of erosive wear were revealed depending on the structural state of the alloy. The obtained results convincingly demonstrate that by means of refining the grain structure of alloys and depositing a protective ion-plasma TiVN coating on the alloy surface, it is possible to significantly increase the erosion resistance of materials operating under high loads and in aggressive environments

Vibronic spectra of bifluorene and terfluorene

Using the method of the density functional theory (DFT/B3LYP/6-31G(d,p)), the vibrational absorption and emission spectra of bifluorene and terfluorene molecules are calculated. A good agreement is obtained between the model and experimental spectra. The vibrational promoting modes forming a vibronic progression in the emission bands are determined