Amorphous Alloys Research Articles

Viscosity of Al–Ni–Co–Nd(Sm) glass-forming melts at high temperatures

Obtaining amorphous alloys with good mechanical and anticorrosion properties is an important problem of modern condensed matter physics. Since the preparation of amorphous alloys involves casting them from liquid state, information on the properties of the melts is needed. Viscosity is one of the most informative structure-sensitive property of melts. In this paper viscosity of some glass-forming Al–Ni–Co–Nd(Sm) melts with different ratio of transition metals was studied using damped oscillation method in a wide temperature range up to 1550 K. Activation energies of the viscous flow were calculated from the experimental data. The hysteresis of viscosity temperature dependences during heating and subsequent cooling was found. It can be associated with a melt transition to a more homogeneous state. The repeated heating and cooling of the melts without crystallization lead to Arrhenius type of viscosity temperature dependences.

Different impact of recovery annealing and thermal pressure treatments on the microstructure and mechanical properties of rejuvenated Cu64Zr36 metallic glasses: A molecular dynamics study

The interpenetrating connection of icosahedra network (ICOIN) was termed as structural skeleton, which could quantify the strength and ductility of MGs. The impact of different rejuvenation methods on medium-range order (MRO) alterations was rarely studied. This work employed molecular dynamics simulations to examine the difference in MRO evolution of metallic glasses treated by recovery annealing and thermal-pressure treatment during uniaxial tension. All of the specimens obtain enhanced ductility due to improved potential energy. During tension, ICOI of all rejuvenated specimens exhibits an increased destruction rate and a decreased transformation rate. However, there are some converse characteristics in the specimens under different rejuvenation methods. The rejuvenated specimens treated by recovery annealing exhibit increased free volume and decreased ICOIN density. After thermal-pressure treatment, the rejuvenated specimens demonstrated decreased free volume and enhanced ICOIN density. During tension, the enhancement of icosahedral free volume in specimens treated by thermal pressure largely decreased the ICOIN density, thereby increasing the ductility. After tension, the rejuvenated specimens under high pressure have a significant reduction in ICOIN density compared to those under recovery annealing. The significance of this work is to accurately regulate the ICOIN density of rejuvenated specimens.

In-depth Analysis of Structural Heterogeneity in High Entropy Bulk Metallic Glasses Using 4D-STEM

In-depth Analysis of Structural Heterogeneity in High Entropy Bulk Metallic Glasses Using 4D-STEM

Unveiling the Formation Mechanism of Medium Range Ordering in Zr-based Bulk Metallic Glasses Using Angular Correlation Analysis of 4D-STEM

Unveiling the Formation Mechanism of Medium Range Ordering in Zr-based Bulk Metallic Glasses Using Angular Correlation Analysis of 4D-STEM

A promising application of bulk metallic glasses in torque sensor

A promising application of bulk metallic glasses in torque sensor

Metallic glasses show promise for bone grafting

Simulations showed that the mechanical and thermophysical properties of metallic glasses could make them an excellent choice for dental grafts.

Various rejuvenation behavior of Cu–Zr–Al-(Sn) metallic glass via deep cryogenic cycling treatment

Deep cryogenic cycling treatment (DCT) has been used to rejuvenate Cu–Zr–Al-(Sn) bulk metallic glasses (BMGs). The thermally treated samples exhibit rejuvenated behaviors characterized by improved enthalpy of relaxation and plasticity. Notably, the degree of rejuvenation varies significantly in Sn-doped samples compared to the Sn-free counterparts. Molecular dynamics simulations reveal that Sn doping leads to a decrease in the peak height of Cu–Zr atom pairs and a significant increase in Zr–Zr atom pairs. The negative mixing heat between Sn and Zr results in the degradation of short-range ordered structures between Cu–Zr, generating the clusters with more Zr atoms and a subsequently more closely packed structure. Such structural modification is associated with the less obvious rejuvenation in Sn-doped samples. Furthermore, the addition of Sn reduces the fraction of polyhedral structures with higher five-fold symmetry, particularly <0, 0, 12, 0>, thereby negatively impacting the rejuvenation behavior during DCT. The changes in microstructure during rejuvenation also influences the shear localization under external shear deformation. The reduction in the proportion of polyhedra with relatively higher five-fold symmetry, such as <0, 0, 12, 0>, leads to a more pronounced activation in local regions. These activated local shear units contribute to the delocalization of shear flow and the initiation of additional shear bands. The present study sheds light on the intricate interplay between Sn doping, microstructural changes, and the resulting mechanical properties in metallic glasses subjected to deep cryogenic cycling.

The effect of particle size on densification and mechanical properties of Fe-based bulk metallic glasses by spark plasma sintering

The effect of particle size on densification and mechanical properties of Fe-based bulk metallic glasses by spark plasma sintering

Increased tensile strength induced by the precipitation of nanocrystals for welding joints of Zr-based amorphous alloys

Zr-based amorphous alloys have attracted intensive attention for applications because of their excellent mechanical property. However, the welding process is inevitable for some special cases, such as the obtain of large size structure parts. It is significant to clarify the influence of introduced welding joints on mechanical properties in Zr-based amorphous alloys. Herein, the increased tensile strength of welding joints in Zr-based amorphous alloys is demonstrated by choosing a suitable initial temperature of Cu cooling fixtures for pulsed laser welding. It is found that an optimized tensile strength is observed when the initial temperature is −20 °C. With the decrease of the initial temperature from 10 to −30 °C, the tensile strength shows a trend of first increasing and then decreasing. Combined with the characterization of microstructures, it can be concluded that the increased tensile strength results from the precipitation of nanocrystals in the heat affected zone. Thus, our results provide a method to improve the mechanical property by controlling the microstructures of the heat affected zone in welding joints of Zr-based amorphous alloys.

Biosafety and osteogenic properties of a new type of absorbable magnesium-based amorphous alloy

The treatment of bone defects has always been a difficult problem in orthopedic clinical practice, and research on new materials is currently a hot topic. In this study, the biological safety and bone induction ability of a new magnesium-based amorphous alloy (Mg66Zn30Ca3Sr1) and zinc–magnesium powder were verified and compared in animal experiments. Thirty Sprague–Dawley rats were randomly divided into three groups, and a bone defect was made in the lateral condyle of the femur of the left hind limb. The blank group closed the wound after establishing the bone defect model, the control group added zinc–magnesium powder and chondroitin sulfate gel, and the experimental group added magnesium–zinc–calcium–strontium alloy and chondroitin sulfate gel with the same volume. Peripheral venous blood of rats was collected at 4, 8, and 12 weeks postoperatively, and alanine aminotransferase (ALT), aspartate transferase, creatinine, blood urea nitrogen, magnesium ion, and zinc ion levels were evaluated. The expression levels of bone morphogenetic protein 2 (BMP-2), osteoprotegerin (OPG), osteopontin (OPN), core binding factor α1 (RUNX2), and alkaline phosphatase (ALP) were detected using enzyme-linked immunosorbent assay (ELISA). After the rats were euthanized, samples were taken. X-rays and micro-computed tomography (CT) images of the bone defect were obtained, and hematoxylin and eosin and Masson staining were performed. This study shows that amorphous magnesium–zinc–calcium–strontium alloy is a biodegradable metal with good biocompatibility and bone induction and has good application prospects in treating bone defects.

Study of Size Effect on Ni60Nb40 Amorphous Particles and Thin Films by Molecular Dynamic Simulations

Ni60Nb40 amorphous particles (APs) and amorphous thin films (ATFs) with various sizes were investigated by molecular dynamic simulations. It is revealed that sample size has effects on both Ni60Nb40 APs and ATFs composed of shell or surface and core components. Ni60Nb40 APs have an average bond length of 2.57 Å with major fivefold-symmetry atomic packing and low bond-orientation orders of Q6 and Q4 in both core and shell components. Ni atoms in Ni60Nb40 APs and ATFs prefer to segregate to the shell and surface regions, respectively. Atomic packing structure differences between various-sized Ni60Nb40 APs and ATFs affect their glass transition temperatures Tg, i.e., Tg decreases as the particle size or the film thickness decreases in Ni60Nb40 APs and ATFs, respectively. Our obtained results for Ni60Nb40 APs and ATFs clearly reveal a size effect on atomic packing and glass transition temperature in low-dimensional metallic glass systems.

Rapidly reversible superwettability on textured metallic surfaces

Reversible superwettability on non-coated metallic surfaces has a broad range of engineering applications, yet achieving a rapid reverse of superwettability is still technically challenging on different metals. Here we show that rapid transition between superhydrophobicity (SHB) /hydrophobicity (HB) and superhydrophilicity (SHL) within tens of minutes can be achieved on femtosecond laser-treated Al surfaces with the assistance of ultraviolet (UV) irradiation and direct-current (DC) sputtering, overcoming traditional challenges posed by Al₂O3 in wettability conversion. The extremely high wettability conversion rate on Al surfaces was found to be related to the formation of textured amorphous metal oxides, whose relative content of oxygen vacancies (OVs) can be more easily changed. In the process of wettability change, there is a linear correlation between the metal surface potential and the cosine value of the contact angle. Our findings provide a versatile approach for designing metal surfaces with rapidly reversible superwettability, enabling various applications such as oil–water separations and the controlled release of hydrophilic drugs.

Crystallization of Metallic Glasses and Supercooled Liquids.

This is an overview of recent findings on the structural changes observed upon heating, including crystallization processes in conventional metallic glasses, bulk metallic glasses, and their corresponding supercooled liquids. This paper encapsulates the various crystallization behaviors in metallic glasses by primary, eutectic, and polymorphous mechanisms, highlighting the complexity and diversity of the nucleation and growth mechanisms involved. Mechanically induced room-temperature crystallization is also discussed.

Kinetics of crystallization and soft magnetic properties of Co72Fe8B10Si10 amorphous alloys

Co72Fe8B10Si10 amorphous alloy was prepared in an Ar atmosphere using a single roller rapid quenching technique at a wheel speed of 25 m/s. The prepared ribbons were annealed for 1 h at temperatures ranging from 473 to 773 K. X-ray diffractometer was used to observe the microstructure transformation. Field emission scanning electron micrographs exhibit mosaic type structures that become more prominent with increasing annealing temperature. Energy dispersive X-ray spectroscopy was also utilized to observe the concentrations of elements. The Kissinger and Ozawa equations were utilized to determine the amorphous alloy's crystallization activation energy. The two methods revealed consistent findings in their calculations. At 473 K, the obtained maximum real initial permeability (μ′max) is 376 which remains unchanged up to 10 kHz, whereas for 573 K, μ′max is noted to be 361 to 100 kHz. Other magnetic parameters such as loss factor, quality factor, and relative quality factor were also investigated for the Co72Fe8B10Si10 amorphous alloy to elucidate its suitability in such materials based devices.

Uncovering the structural origin of shear banding in metallic glasses via tracing back to the critical glass transition process

Uncovering the structural origin of shear banding in metallic glasses via tracing back to the critical glass transition process

Comparative Analysis of Microabrasive Film Finishing Effects across Various Process Variants.

The paper investigates various methods of microfinishing and arrives at the best technique to produce a very smooth surface. Various setups, with and without oscillation, were developed, together with a microfinishing attachment used on conventional lathes and milling machines. The workpiece material used was an amorphous nickel-phosphorus Ni-P alloy. The surface roughness parameters, such as Sa, Sv, and Sp, were measured with the TalySurf CCI6000 instrument. For the measurement of the surface protrusions, an "analysis of islands" technique was used at various levels of cut-off. The 2BA method-machining below the workpiece axis with oscillation-turned out to be the most effective method applied because it had the highest density of protrusions while having the smallest value of surface roughness. Non-oscillation with the machining zone below the axis also becomes effective, indicating that repositioning can compensate for a lack of oscillation. Already, the very compact surface structure achieved with minimized depths in the valleys by the 2BA method supported the improvement in tribological performance and increase in load-carrying capacity, together with lubricant retention enhancement. These results show that the microfinishing process can be optimized by parameter tuning, and also, non-oscillating methods could come to be a practical alternative, probably reducing the complexity of equipment and cutting costs. Further studies need to be aimed at the scalability of these methods and their application to other materials and fields.

Performance investigation of the artificial aggregate by integrally recycling incineration bottom ash and fly ash

The potential expansion risks caused by the reaction of metallic aluminum and glass particles in incineration bottom ash (IBA) in high-alkalinity environments limit its use as an aggregate in concrete applications. This study aims to develop artificial aggregates (AAs) by integrating IBA with a low-alkalinity binder comprising incineration fly ash (IFA) and blast furnace slag (GGBS). The synergetic effects of using IBA with IFA-GGBS binders in AAs are investigated and compared to integrating IBA with IFA-OPC binders. The impacts of IFA and IBA contents on physico-mechanical properties and mineralogical characteristics of AAs are also assessed. The results show that AAs achieve a loose bulk density ranging from 890 to 1072 kg/m3, with the highest strength of 5.7 MPa recorded for GGBS-based aggregates with 40 % IBA. The pozzolanic reaction of GGBS-IFA contributes to a robust binder that facilitates interlocking within the system. The relatively low alkalinity associated with the pozzolanic reaction between GGBS and IFA suppresses the potential expansion reaction, ensuring the safe application of AAs in concrete. Moreover, the internal curing of GGBS-based AAs and their interaction with the cement matrix densify the microstructure of the interface transition zone, resulting in excellent compressive strength of AAs-contained concrete (>45 MPa), which surpasses that of conventional concrete.

Synchronously improving glass forming ability and mechanical properties by Pd alloying Zr-Al-Cu bulk metallic glass

In this work, the influences of Pd addition on the glass-forming ability (GFA), thermal behaviors, mechanical properties and microstructure of the Zr60Al10Cu30 bulk metallic glasses (BMGs) were systematically investigated. Our study shows that proper addition of Pd can simultaneously improve the GFA, strength and plasticity of BMGs. The BMGs with Pd contents of 2.5 at.% and 5 at.% exhibit high GFA of 10 mm and 12 mm, high strength of 1852 MPa and 1858 MPa, and good plasticity of 4.3 % and 5.9 %, respectively, all of them are much higher than those of Zr60Al10Cu30 BMGs. It is revealed that alloying BMGs with proper Pd promotes the formation of a higher degree of icosahedral clusters, which is responsible for improved GFA and strength, and simultaneously encourages a decrease in the volume of shear transition zone (STZ) and the amount of imperfect ordered packing (IOP) clusters, which are responsible for the enhanced plasticity. Our findings indicate that the synergistic effect of short-range ordered structures induced by alloying amorphous alloys plays an important role in simultaneously improving the GFA and mechanical properties, providing valuable insights for BMG design.

Product classes characterization at micro-scale level applied to granular wastes fractions < 20 mm: a case-study

A product class characterization was requested on some plastic granular waste samples, already reduced in fine form with particles < 20 mm, derived from waste electrical wires and PC cables. The product class discrimination was worked out by visual characterization with the aid of optical stereomicroscopy and confirmation by electron scanning microscopy (SEM) and microanalysis. Characterization at a micro-scale level evidenced predominance of plastic materials with presence of metal wires, paper, textile and glass fibres at residual levels in the main fraction (0.5–4 mm). The fractions < 0.5 mm, when present, cannot easily be distinguished at sight and only approximate qualitative information can be extracted by SEM analysis. The described approach has been carried out effectively due to major shape and material differences between plastic particles and metal wires and other materials. However, this approach may not work in every case, or it may not lead to usable results with every type of waste.

Unveiling the asymmetry in density within the shear bands of metallic glasses

Unveiling the asymmetry in density within the shear bands of metallic glasses