Deformation behavior of thermally rejuvenated Zr-Cu-Al-(Ti) bulk metallic glass.

The deformation behavior of metallic glasses has been shown in prior studies to be often dependent on its structural state, namely higher energy "rejuvenated" state versus lower energy "relaxed" state. Here, the deformation behavior of thermally rejuvenated Zr-Cu-Al-(Ti) bulk metallic glasses (BMGs) was evaluated. Rejuvenation was achieved by cryogenic thermal cycling with increase of free volume measured in terms of enthalpy of relaxation.

Biocompatible Co-P Metallic Glasses with Superior Degradation Tolerance in Physiological Environments.

Metallic glasses represent a class of metallic alloys with a fully amorphous structure and attractive properties, making them promising in bioimplant applications. Here, the degradation tolerance of biocompatible cobalt-phosphorus (Co-P) metallic glasses was studied in a simulated physiological environment. The metallic glasses were synthesized in the form of coatings through a facile electrodeposition approach.

Phase-Specific Damage Tolerance of a Eutectic High Entropy Alloy.

Phase-specific damage tolerance was investigated for the AlCoCrFeNi high entropy alloy with a lamellar microstructure of L1 and B2 phases. A microcantilever bending technique was utilized with notches milled in each of the two phases as well as at the phase boundary. The L1 phase exhibited superior bending strength, strain hardening, and plastic deformation, while the B2 phase showed limited damage tolerance during bending due to micro-crack formation.

Molten Salt Corrosion Behavior of Dual-Phase High Entropy Alloy for Concentrating Solar Power Systems.

Dual-phase high entropy alloys have recently attracted widespread attention as advanced structural materials due to their unique microstructure, excellent mechanical properties, and corrosion resistance. However, their molten salt corrosion behavior has not been reported, which is critical in evaluating their application merit in the areas of concentrating solar power and nuclear energy. Here, the molten salt corrosion behavior of AlCoCrFeNi eutectic high-entropy alloy (EHEA) was evaluated in molten NaCl-KCl-MgCl salt at 450 °C and 650 °C in comparison to conventional duplex stainless steel 2205 (DS2205).

Model Metallic Glasses for Superior Electrocatalytic Performance in a Hydrogen Oxidation Reaction.

Metallic glasses or amorphous alloys, with their excellent chemical stability, disordered atomic arrangement, and ability for thermoplastic nanostructuring, show promising performance toward a range of electrocatalytic reactions in proton-exchange membrane fuel cells. However, there are knowledge gaps and a distinct lack of understanding of the role of amorphous alloy chemistry in determining their catalytic activity. Here, we demonstrate the influence of alloy chemistry and the associated electronic structure on the hydrogen oxidation reaction (HOR) activity of a systematic series of PtPdCuNiP bulk metallic glasses (BMGs) with = 0 to 42.

Effect of composition and thermal history on deformation behavior and cluster connections in model bulk metallic glasses.

The compositional dependence and influence of relaxation state on the deformation behavior of a Pt-Pd-based bulk metallic glasses model system was investigated, where platinum is systematically replaced by topologically equivalent palladium atoms. The hardness and modulus increased with rising Pd content as well as by annealing below the glass transition temperature. Decreasing strain-rate sensitivity and increasing serration length are observed in nano indentation with increase in Pd content as well as thermal relaxation.

Excellent ballistic impact resistance of AlCoCrFeNi multi-principal element alloy with unique bimodal microstructure.

Multi-principal element alloys represent a new paradigm in structural alloy design with superior mechanical properties and promising ballistic performance. Here, the mechanical response of AlCoCrFeNi alloy, with unique bimodal microstructure, was evaluated at quasistatic, dynamic, and ballistic strain rates. The microstructure after quasistatic deformation was dominated by highly deformed grains.

Unraveling the Structural Statistics and Its Relationship with Mechanical Properties in Metallic Glasses.

Metallic glasses exhibit excellent properties such as ultrahigh strength and excellent wear and corrosion resistance, but there is limited understanding on the relationship between their atomic structure and mechanical properties as a function of their structural state. In this paper, we bridge the processing-structure-property gap by utilizing molecular dynamics simulation for a model binary metallic glass, namely NiP. The structural statistics including the fraction of Voronoi index, the distribution of Voronoi volume, and medium-range ordering are calculated to explain the observed changes in mechanical behavior and strain localization upon relaxation and rejuvenation.

Multiscale Manufacturing of Amorphous Alloys by a Facile Electrodeposition Approach and Their Property Dependence on the Local Atomic Order.

Metallic glasses are a unique class of materials combining ultrahigh strength together with plastic-like processing ability. However, the currently used melt quenching route to obtain amorphous alloys has a high cost basis in terms of manufacturing and expensive constituent elements often necessary to achieve the glassy state, thus hindering widespread adoption. In contrast, multimaterial electrodeposition offers a low-cost and versatile alternative to obtain amorphous alloys.

Biocompatible High Entropy Alloys with Excellent Degradation Resistance in a Simulated Physiological Environment.

Bioimplants are susceptible to simultaneous wear and corrosion degradation in the aggressive physiological environment. High entropy alloys with equimolar proportion of constituent elements represent a unique alloy design strategy for developing bioimplants due to their attractive mechanical properties, superior wear, and corrosion resistance. In this study, the tribo-corrosion behavior of an equiatomic MoNbTaTiZr high entropy alloy consisting of all biocompatible elements was evaluated and compared with 304 stainless steel as a benchmark.

Dynamic Shear Deformation of a Precipitation Hardened AlCoCrFeNi Eutectic High-Entropy Alloy Using Hat-Shaped Specimen Geometry.

Lamellar eutectic structure in AlCoCrFeNi high-entropy alloy (HEA) is emerging as a promising candidate for structural applications because of its high strength-ductility combination. The alloy consists of a fine-scale lamellar + B2 microstructure with high flow stresses > 1300 MPa under quasi-static tensile deformation and >10% ductility. The response to shear loading was not investigated so far.

High-Temperature Nano-Indentation Creep of Reduced Activity High Entropy Alloys Based on 4-5-6 Elemental Palette.

There is a strong demand for materials with inherently high creep resistance in the harsh environment of next-generation nuclear reactors. High entropy alloys have drawn intense attention in this regard due to their excellent elevated temperature properties and irradiation resistance. Here, the time-dependent plastic deformation behavior of two refractory high entropy alloys was investigated, namely HfTaTiVZr and TaTiVWZr.

Enhanced Biocorrosion Resistance and Cellular Response of a Dual-Phase High Entropy Alloy through Reduced Elemental Heterogeneity.

The leaching out of toxic elements from metallic bioimplants has serious repercussions, including allergies, peripheral neuritis, cancer, and Alzheimer's disease, leading to revision or replacement surgeries. The development of advanced structural materials with excellent biocompatibility and superior corrosion resistance in the physiological environment holds great significance. High entropy alloys (HEAs) with a huge compositional design space and outstanding mechanical and functional properties can be promising for bioimplant applications.

Small-scale mechanical behavior of a eutectic high entropy alloy.

Eutectic high entropy alloys, with lamellar arrangement of solid solution phases, represent a new paradigm for simultaneously achieving high strength and ductility, thereby circumventing this well-known trade-off in conventional alloys. However, dynamic strengthening mechanisms and phase-boundary interactions during external loading remain unclear for these eutectic systems. In this study, small-scale mechanical behavior was evaluated for AlCoCrFeNi eutectic high entropy alloy, consisting of a lamellar arrangement of L1 and B2 solid-solution phases.

Noble-Metal based Metallic Glasses as Highly Catalytic Materials for Hydrogen Oxidation Reaction in Fuel Cells.

Electro-catalyst design with superior performance and reduced precious metal content (compared to state-of-the-art Pt/C) has been a challenge in proton exchange membrane fuel cells, preventing their widespread adoption. Metallic glasses have recently shown promising performance and large electrochemical surface area in catalytic reactions. The electro-catalytic behavior of recently developed Pt-, Pd-, and Pt/Pd-based metallic glasses was evaluated in this study using scanning electrochemical microscopy.

Small-Scale Plastic Deformation of Nanocrystalline High Entropy Alloy.

High entropy alloys (HEAs) have attracted widespread interest due to their unique properties at many different length-scales. Here, we report the fabrication of nanocrystalline (NC) AlCoCrFeNi high entropy alloy and subsequent small-scale plastic deformation behavior via nano-pillar compression tests. Exceptional strength was realized for the NC HEA compared to pure Ni of similar grain sizes.

Electrochemical and Friction Characteristics of Metallic Glass Composites at the Microstructural Length-scales.

Metallic glass composites represent a unique alloy design strategy comprising of in situ crystalline dendrites in an amorphous matrix to achieve damage tolerance unseen in conventional structural materials. They are promising for a range of advanced applications including spacecraft gears, high-performance sporting goods and bio-implants, all of which demand high surface degradation resistance. Here, we evaluated the phase-specific electrochemical and friction characteristics of a Zr-based metallic glass composite, ZrTiNbCuNiBe, which comprised roughly of 40% by volume crystalline dendrites in an amorphous matrix.

Exceptionally high cavitation erosion and corrosion resistance of a high entropy alloy.

Cavitation erosion and corrosion of structural materials are serious concerns for marine and offshore industries. Durability and performance of marine components are severely impaired due to degradation from erosion and corrosion. Utilization of advanced structural materials can play a vital role in limiting such degradation.

Spin-exchange interaction between transition metals and metalloids in soft-ferromagnetic metallic glasses.

High-performance magnetic materials have immense industrial and scientific importance in wide-ranging electronic, electromechanical, and medical device technologies. Metallic glasses with a fully amorphous structure are particularly suited for advanced soft-magnetic applications. However, fundamental scientific understanding is lacking for the spin-exchange interaction between metal and metalloid atoms, which typically constitute a metallic glass.

Guided Evolution of Bulk Metallic Glass Nanostructures: A Platform for Designing 3D Electrocatalytic Surfaces.

Electrochemical devices such as fuel cells, electrolyzers, lithium-air batteries, and pseudocapacitors are expected to play a major role in energy conversion/storage in the near future. Here, it is demonstrated how desirable bulk metallic glass compositions can be obtained using a combinatorial approach and it is shown that these alloys can serve as a platform technology for a wide variety of electrochemical applications through several surface modification techniques.

Controlling the length scale and distribution of the ductile phase in metallic glass composites through friction stir processing.

We demonstrate the refinement and uniform distribution of the crystalline dendritic phase by friction stir processing (FSP) of titanium based ductile-phase reinforced metallic glass composite. The average size of the dendrites was reduced by almost a factor of five (from 24 m to 5 m) for the highest tool rotational speed of 900 rpm. The large inter-connected dendrites become more fragmented with increased circularity after processing.