Bulk Metallic Alloys Research Articles

A quasi-2D integrated experimental–numerical approach to high-fidelity mechanical analysis of metallic microstructures

Integrated experimental–numerical testing on bulk metal alloys with fine, complex microstructures is known to be highly challenging, since measurements are restricted to the sample surface, thereby failing to capture the effects of the 3D subsurface microstructure. Consequently, a quantitative comparison of deformation fields between experiments and simulations is hardly possible. To overcome this, we propose a novel ‘quasi-2D’ integrated experimental–numerical testing methodology that hinges on the fabrication of μm-thin specimens with practically through-thickness microstructures over large regions of >100 μm. The specimens are fully characterized from both surfaces and tested in-situ to retrieve microstructure-resolved deformation fields. Simultaneously, the full microstructure is discretized in 3D and simulated. This allows for a detailed, one-to-one quantitative comparison of deformation fields between experiments and simulations, with negligible uncertainty in the subsurface microstructure. Consequently, a degree of agreement between experiments and simulations is attained which we believe to be unprecedented at this scale. We demonstrate the capabilities of the framework on polycrystalline ferritic steel and dual-phase ferritic–martensitic steel specimens. At the mesoscale, the methodology enables quantitative comparisons of the interaction between multiple grains, while, at the microscale, it enables advancement of numerical models by direct confrontation with detailed experimental observations. Specifically, it is revealed that the individual slip system activity maps, identified with SSLIP, near a grain boundary can only be reasonably predicted by enhancing the adopted crystal plasticity simulations with a discrete slip plane model. Additionally, the experimentally observed strong anisotropic plasticity of martensite can only be captured with a substructure-enriched crystal plasticity model.

Role of vacancies in structural thermalization of binary and high-entropy alloys

Vacancy assisted atomic self-diffusion is a major structural thermalization mechanism in bulk metal alloys. Depending on alloy composition, the local atomic environments might stabilize vacancies to such extent that the vacancies become trapped and the atomic self-diffusion part of the thermalization process stalls. The consequence is that such alloys get kinetically trapped in disordered structures. In this study, we investigate equimolar AgAu, CuPt, AgPdPtIr, and AgAuCuPdPt alloy thermalizing using Metropolis Monte Carlo simulations in two approaches, one where the alloy structure changes through vacancy migration and one where the structure changes by swapping atomic pairs. By comparing the two approaches, we find that the vacancy is less effective at thermalizing alloys with more elements (i.e. AgPdPtIr and AgAuCuPdPt), more heterogeneous configurational internal energy distributions (i.e. CuPt and AgPdPtIr), and strong interactions between certain elements, e.g. Ir-Ir interactions in AgPdPtIr. In the case of AgPdPtIr, the vacancy cannot thermalize Ir-Ir neighbors even when the vacancy is mobile, because the vacancy has difficulty breaking individual Ir-Ir pairs apart.

Biocompatible hydroxyapatite ceramic coating on titanium alloys by electrochemical methods via Growing Integration Layers [GIL] strategy: A review

The purpose of this review paper is to describe a noble approach, called Growing Integration Layers (GIL) method, for the application of biocompatible oxide ceramics layers coating on bulk metallic alloys. Since these oxides are utilizing component(s) of the alloy then formed by mostly electrochemical reactions at low temperatures, they are well adhered on the alloy substrate. The GIL strategy differs significantly from so-called layer-by-layer integration, layers are deposited from top-to-top. In the GIL, the oxide layers are produced and grown on the substrate alloy from the bottom. Therefore those layers on metallic substrate is chemically and structurally continuous thus shows excellent adhesion. Using GIL method, a variety of functional and structural ceramic layers can be processed mostly in aqueous solutions, thus they are typical soft and green processes, consuming low energy. These methods can be applied in the preparation of dense/porous and graded intermediate layers of ceramics for a wide variety of applications, including thermal, mechanical, chemical and biomedical. This review concentrate on successful ceramics coating on Titanium based metallic alloys via GIL strategy. The GIL technology improves the adhesion of ceramic layers and introduces bioactivity to bulk metallic alloys. Since bulk metallic glasses and alloys generally contain active components like titanium, it can be used in the formation of titanium oxide and/or hydroxides which are bioactive. During this oxidation/hydroxidation, widely diffused interfaces and continuously graded layers are formed from bulk substrate, even at ambient temperature and pressure. One of the most notable examples of GIL method is the coating of bio-active hydroxyapatite (HA) ceramics on Ti alloys. We have exhibited here with (1) Bioactive ceramic layers on bulk metallic glasses, (2) Hydroxyapatite-like coating on Ti–Cu–Sn alloy and (3) Sr doped apatite-like coating on the same alloy.

Exchange interaction between localized magnetic moments and conduction-electrons in Er doped gold nanoparticles synthesized by laser ablation in water

In this work, we report a fundamental study on the exchange interaction between localized rare earth magnetic moments and conduction electrons of Er3+ diluted in Au metallic nanoparticles (NPs) produced by laser ablation in liquid. The study was carried out in Au1−xErx (x ≤ 0.026) bulk metallic alloys and NPs with a mean size of 20 nm. The samples were characterized by means of x-ray diffraction, transmission electron microscopy, magnetic susceptibility, and electron spin resonance (ESR) experiments. The obtained results showed that, despite the high temperature and being far away from chemical equilibrium throughout the laser ablation process, in the AuNPs, the Er3+ (J = 15/2) ground state of the crystal electric field split multiplet remains a Γ7 (g = 6.79) Kramers doublet with the expected g-shift and T-dependence of the ESR linewidth, preserving the general bulk properties and the cubic symmetry. In addition, the Au1−xErx NPs present narrow ESR residual linewidth suggesting homogeneous Er3+ doping and negligible strain distribution in the Au1−xErx NPs. This new methodology may certainly provide relevant insight into the study of the intrinsic physical properties of dilute rare earth metallic alloys at the nanometer scale seeking quantum size effects and motivates novel technological applications.

Compositions design of Co-Fe-based bulk metallic alloys

Glass forming ability (GFA) is one of the key factors hindering the application of bulk metallic glasses (BMGs). In this paper, a cluster-related method was used to design good glass-formers in the complex Co-Fe-based system. A novel Co-centered Co-Mo binary topologically packed cluster Co-Co8Mo4 with 12-coordination number was found and used. The basic ternary composition in Co-Mo-B system is calculated based on an intersection of cluster lines B-B2Co8 and Co-Co8Mo4. Based on this, a series of novel Co-Fe-based glass-formers with high GFA, were quickly designed using the method of similar element replacement and microalloying. The best glass-former is (Co27.5Fe27.5Mo12.2Cr12.2B16P4.6)98Y2. The source of high GFA of designed glass-formers was also discussed. The results of this paper would offer researchers a novel insight in understanding the source of high GFA of Co/Fe-based system, and lay a solid foundation for exploring Co/Fe-Mo-based glass-formers via newly found Co-Mo binary cluster.

Ultrasonic brazing of Zr-based bulk metallic glass and 1060 Al alloy using Zn-3Al filler metal

Ultrasonic brazing of Zr-based bulk metallic glasses (Zr-BMG) and 1060-Al alloy dissimilar was realized by using a Zn-3Al filler metal. A firm metallurgical bonding was obtained at the dissimilar joint interfaces. In the initial stage, a single-phased Zn50Al25Zr25 IMC layer was found on the Zr-BMG surface. Prolonging the brazing time, the excessive growth of the Zn50Al25Zr25 IMC layer inhibited the diffusion of Al from brazing seam to the reaction front, which induced the composition fluctuation of Al and thus the formation of Zn50Al25Zr25/Zn-rich phase composite layers on the Zr-BMG surface. The shear strength of joints was affected by the interfacial reaction phase, and the highest value obtained was 68 MPa.

A ‘virtual sensing’ framework for µECM/hybrid laser- µECM for monitoring interelectrode gap conditions

Micro-ECM (µECM) has capability to process wide class of conductive materials ranging from metals, cermets to bulk metallic glasses and shape memory alloys. The process efficiency and speed is further enhanced by hybridization of micro-ECM process with laser which can act as a localized heat source or a cutting energy source depending on the fluence on the workpiece surface. The hybridization of micro-ECM with laser facilitates machining of materials/alloys with conductivity variations and promotes their uniform dissolution. The process mechanism involves several multiphysics phenomena occurring in the interelectrode gap (IEG) which is of the order of 20-50 µm. The technological limitations of putting sensors in this small IEG limits the monitoring of physical quantities (such as temperature, hydrogen and oxygen gas volume fraction, electrolyte conductivity, current density on workpiece surface) during the process. However, these physical quantities can be effectively estimated by multiphysics simulations.At first, the experimental experience with different sensors (temperature sensor, current sensor, high speed imaging and particle image velocimetry (PIV)) is presented for µECM/hybrid laser-µECM process and their limitations are discussed. Subsequently, this work proposes a ‘virtual sensing’ approach enabled by multiphysics simulations. A detailed multiphysics model is developed in Comsol® software which models several phenomena occurring in µECM/hybrid laser-µECM process such as temperature-dependent electrolyte properties, hydrogen and oxygen gas generation, heat generation due to joule heating and laser heating, laminar fluid flow and electric currents. The properties are evaluated at 5 different (virtual sensor) locations inside the IEG, more specifically on the workpiece surface, tool surface, in the center of IEG, just at the exit of IEG and at a specified location. These virtual sensors are implemented in the Comsol® software by employing a dynamic point probe which probes the model-solution at a defined point in a moving geometry. The evolution of the aforementioned parameters in the IEG is monitored and supported by fundamental explanations as well as observational experiments. This research is a first step towards facilitating predictive sensing of ECM and allied multiphysics processes thereby supporting process design and minimizing experimental efforts by virtual process monitoring.

Enabling Superhydrophobicity-Guided Superwicking in Metal Alloys via a Nanosecond Laser-Based Surface Treatment Method.

Enabling capillary wicking on bulk metal alloys is challenging due to processing complexity at different size scales. This work presents a laser-chemical surface treatment to fabricate superwicking patterns guided by a superhydrophobic region over a large-area metal alloy surface. The laser-chemical surface treatment generates surface micro/nanostructures and desirable surface chemistry simultaneously. The superhydrophobic surface was first fabricated over the whole surface by laser treatment under water confinement and fluorosilane treatment; subsequently, superwicking stripes were processed by a second laser treatment in air and cyanosilane treatment. The resultant surface shows superwicking regions surrounded by superhydrophobic regions. During the process, superwicking regions possess dual-scale structures and polar nitrile surface chemistry. In contrast, random nanoscale structures and fluorocarbon chemistry are generated on the superhydrophobic region of the aluminum alloy 6061 substrates. The resultant superwicking region demonstrates self-propelling anti-gravity liquid transport for methanol and water. The combination of the capillary effect of the dual-scale surface microgrooves and the water affinitive nitrile group contributes toward the self-propelling movement of water and methanol at the superwicking region. The initial phase of wicking followed Washburn dynamics, whereas it entered a non-linear regime in the later phase. The wicking height and rate are regulated by microgroove geometry and spacing.

Measurement Technique for Microwave Surface Resistance of Additive Manufactured Metals

Additive manufactured (AM) metals are a subject of much interest for their performance in passive microwave applications. However, limitations could arise due to artifacts, such as surface texture and/or roughness resulting from the manufacturing process. We have, therefore, adopted a parallel plate microwave resonator for the accurate measurement of the surface resistance of flat metal plates, allowing for microwave current flow in two orthogonal directions by simply exciting a different resonant mode (at 5.3 and 6.4 GHz), without the need to remove and refix the sample. The systematic and random errors associated with the measurement of surface resistance are very small, less than 1% and 0.1%, respectively. The technique is demonstrated with measurements on a range of samples of the alloys, AlSi10Mg and Ti6Al4V, manufactured by laser powder bed fusion, in addition to traditionally machined samples of bulk metal alloys of aluminum and brass. For AM samples of AlSi10Mg, we have studied the effect on the surface resistance of directional roughness features, generated by the laser raster paths, in directions transverse or parallel to microwave current flow. Importantly for passive microwave device applications, we demonstrate that these samples exhibit no systematic anisotropy of surface resistance associated with such surface features.

Simulation of Thermal Field in Bulk Amorphous Steels

Bulk amorphous steels (BASs) have shown great potential for some structural applications due to very attractive physical, thermal and mechanical properties. This paper presents some results for numerical simulation of the thermal field developed during rapid cooling of Fe-Cr-Co-Mo-Y-C-B alloy, to obtain bulk amorphous steels. Rapid cooling technology gives the possibility to obtain bulk metallic alloys with an amorphous structure under conventional industrial conditions, using, for example, commercial-grade raw materials, low vacuum, conventional casting techniques, etc. Once the model being validate, it can be used to optimize the rapid cooling process and casting mold geometry to be able to investigate the possibility to obtain larger bulk amorphous steel components.

Bulk Metal Alloys as a Precursor of Dispersed Particles Catalyzing Growth of Carbon Nanofibers

Bulk Metal Alloys as a Precursor of Dispersed Particles Catalyzing Growth of Carbon Nanofibers

Direct measurement of local constitutive relations, at the micrometre scale, in bulk metallic alloys

Multiscale models involving crystal plasticity are essential to predict the elastoplastic behavior of structural materials with respect to their microstructure. However, those models are often limited by a poor knowledge of the local constitutive behavior. This article reports a method to measure the mechanical behavior directly, at the micrometre scale, in bulk crystalline materials. Local strain and stress states were evaluated at the surface of a bent stainless steel crystal by combining total strain measurements – performed with the digital image correlation technique on optical images – with elastic strain measurements obtained by Laue microdiffraction. A local constitutive relation was measured, in an efficient nondestructive way, without the need for full-field simulations. The method was validated by a comparison between the measured local behavior and the macroscopic behavior of the single crystal.

Peculiarities and usefulness of multicomponent bulk metallic alloys

This paper reviews the peculiarities of multicomponent metastable metallic alloys leading to the syntheses of bulk metallic glasses (BMGs), high entropy BMGs and pseudo high entropy BMGs which cannot be obtained for ordinary component alloys, in addition to the introduction of the features on structure, fundamental and engineering properties and applications for the first type BMGs. The recent extension of multicomponent alloy design has created a new type of metastable alloys such as high entropy BMGs, high entropy crystalline alloys and pseudo-high entropy BMGs with unique atomic configurations and fundamental and engineering properties resulting from multicomponent effect. Considering the diversity of alloy component and composition for multicomponent alloys, the new type of multicomponent metastable metallic alloys are promising for future highly functional engineering materials.

Molecular dynamics simulations of glass formation and atomic structures in Zr60Cu20Fe20 ternary bulk metallic alloy

In this study, the atomic structures and the glass formation process of Zr60Cu20Fe20 ternary bulk metallic alloy were studied by molecular dynamics simulation using the many body tight-binding potentials. In order to investigate glass transition, the specific heat, enthalpy, radial distribution functions, and coordination number were used. The local atomic order in the ternary Zr60Cu20Fe20 was been analyzed using Honeycutt-Andersen pair analysis technique, the distribution of bond-angles and Voronoi analysis. The results show that Zr60Cu20Fe20 alloy begins to transform into a glass, the temperature decreased rapidly to ∼1000 K, and Cu and Fe atoms play important role in the formation of icosahedra environment in alloy.

A high-stability non-contact dilatometer for low-amplitude temperature-modulated measurements.

Temperature modulated thermophysical measurements can deliver valuable insights into the phase transformation behavior of many different materials. While especially for non-metallic systems at low temperatures numerous powerful methods exist, no high-temperature device suitable for modulated measurements of bulk metallic alloy samples is available for routine use. In this work a dilatometer for temperature modulated isothermal and non-isothermal measurements in the temperature range from room temperature to 1300 K is presented. The length measuring system is based on a two-beam Michelson laser interferometer with an incremental resolution of 20 pm. The non-contact measurement principle allows for resolving sinusoidal length change signals with amplitudes in the sub-500 nm range and physically decouples the length measuring system from the temperature modulation and heating control. To demonstrate the low-amplitude capabilities, results for the thermal expansion of nickel for two different modulation frequencies are presented. These results prove that the novel method can be used to routinely resolve length-change signals of metallic samples with temperature amplitudes well below 1 K. This high resolution in combination with the non-contact measurement principle significantly extends the application range of modulated dilatometry towards high-stability phase transformation measurements on complex alloys.

Editorial

Dear Readers, Welcome to the first issue of Advanced Engineering Materials in 2015. Times are changing and so does the field of engineering materials. However, one trend remains the same – we receive more and more submissions each year. Over the last three years the number of submissions has increased by 75%. Such an enormous growth in submissions means that we are forced to become even more selective, so the rejection rate is increasing accordingly. At the same time we aim at providing decisions as fast as possible and have reduced the average time it takes to receive an initial decision to below 30 days Since January 2014 AEM is published online only. One year later we can say that this change is seen very positive throughout the community. Especially the fact that color reproduction of figures is now free has been welcomed by our authors. Advanced Engineering Materials publishes manuscripts from a variety of fields, such as metal foams, bulk metallic glasses, advanced ceramics, alloys, metals, and polymers for a diversity of possible applications. Our authors discuss novel design concepts and new ways to analyze materials properties, including both experimental and modeling approaches. This broad range of topics is also reflected in the list of the most accessed articles in 2014 given in Table 1. Finally, it is my pleasure to welcome the following high-ranking scientists to the advisory board: John Banhart (Helmholtz-Zentrum Berlin), Irene Beyerlein (Los Alamos National Laboratory), Jiang Chang (Shanghai Institute of Ceramics), Elisabetta Comini (Università di Brescia), Sylvain Deville (CNRS, Cavaillon), David Dunand (Northwestern University, Evanston), Juri Estrin (Monash University), Frederik Krebs (Technical University of Denmark, Roskilde), Jamie Kruzic (Oregon State University), Jinsong Leng (Harbin Institute of Technology), Jörg Löffler (ETH Zürich), Zhaoping Lu (University of Science and Technology Beijing), Joao Mano (University of Minho), Alison McMillan (Glyndwr University), Greg Swain (Michigan State University), Candan Tamerler (University of Kansas), Nobuhiro Tsuji (Kyoto University), Jiang-ping Tu (Zhejiang University), Ruslan Z. Valiev (Ufa State Aviation Technical University), Zuankai Wang (City University of Hong Kong), Zhe-Feng Zhang (Shenyang National Laboratory for Materials Sciences), and Ehrenfried Zschech (Fraunhofer Institute for Ceramic Technologies and Systems IKTS, Dresden). We look forward to an ongoing fruitful cooperation with our Advisory Board Members. We look forward to presenting you also in the future the most interesting scientific advances in the field of engineering materials. Sandra Kalveram

An environment-dependent semi-empirical tight binding model suitable for electron transport in bulk metals, metal alloys, metallic interfaces, and metallic nanostructures. II. Application—Effect of quantum confinement and homogeneous strain on Cu conductance

The Semi-Empirical tight binding model developed in Part I Hegde et al. [J. Appl. Phys. 115, 123703 (2014)] is applied to metal transport problems of current relevance in Part II. A systematic study of the effect of quantum confinement, transport orientation, and homogeneous strain on electronic transport properties of Cu is carried out. It is found that quantum confinement from bulk to nanowire boundary conditions leads to significant anisotropy in conductance of Cu along different transport orientations. Compressive homogeneous strain is found to reduce resistivity by increasing the density of conducting modes in Cu. The [110] transport orientation in Cu nanowires is found to be the most favorable for mitigating conductivity degradation since it shows least reduction in conductance with confinement and responds most favorably to compressive strain.

An environment-dependent semi-empirical tight binding model suitable for electron transport in bulk metals, metal alloys, metallic interfaces, and metallic nanostructures. I. Model and validation

Semi-empirical Tight Binding (TB) is known to be a scalable and accurate atomistic representation for electron transport for realistically extended nano-scaled semiconductor devices that might contain millions of atoms. In this paper, an environment-aware and transferable TB model suitable for electronic structure and transport simulations in technologically relevant metals, metallic alloys, metal nanostructures, and metallic interface systems are described. Part I of this paper describes the development and validation of the new TB model. The new model incorporates intra-atomic diagonal and off-diagonal elements for implicit self-consistency and greater transferability across bonding environments. The dependence of the on-site energies on strain has been obtained by appealing to the Moments Theorem that links closed electron paths in the system to energy moments of angular momentum resolved local density of states obtained ab initio. The model matches self-consistent density functional theory electronic structure results for bulk face centered cubic metals with and without strain, metallic alloys, metallic interfaces, and metallic nanostructures with high accuracy and can be used in predictive electronic structure and transport problems in metallic systems at realistically extended length scales.

Non-localized deformation in metallic alloys with amorphous structure

In bulk or ribbon metallic alloys with monolithic amorphous structure, plastic deformation at room temperature is dominated by highly localized shear banding. Here we report suppressed shear localization under tension in a metallic glass (MG) embedded with pre-existing amorphous shear bands using large-scale atomistic simulations. It is demonstrated that pre-deformation lowers material strength and triggers enhanced strain fluctuation before sample yielding, leading to highly dispersed plastic shearing in the entire sample. Furthermore, the transition in deformation mode from highly localized shear banding to non-localized plastic deformation is associated with the competition between the yield strength of the material and the critical stress required for the formation of mature shear bands in the load-bearing materials. Given that a sufficient amount of glassy heterogeneities can be introduced into MGs under experimental conditions, the obtained results could provide a promising strategy for designing tensile ductile MGs with pure amorphous structure at room temperature.

Preparation and characterization of Zr-based bulk metallic glasses in form of plate

Zr-based bulk metallic glasses present an interesting combination of physical, chemical and mechanical properties. During the last decade, intensive progress has been made and a number of applications have been suggested for these materials. In order to successfully apply these materials, it is necessary to accurately characterize their structure, thermal stability and other properties accurately.The aim of the presented work is the manufacturing, examination of the structure of selected Zr-based bulk metallic alloys and confirmation of an amorphous structure using X-ray analysis, microscopic observation and thermal analysis.In this work, the Zr-based bulk metallic glasses in form of plate was successful produced by die pressure casting method. Designed scientific station for casting zirconium based amorphous alloys in the form of plates and rods with selected dimensions is in our university a comprehensive method for achieving amorphous materials which enables us to maintain repeatability of as-cast samples with the amorphous structure and the assumed dimensions range.The diffraction pattern and exothermic reaction as well as the fracture surface morphology reveal that studied as-cast Zr-based alloy is in amorphous state. The calculated GFA parameters show that the alloy exhibits satisfactory glass-forming ability in form of studied plate. These obtained values can suggest that studied alloys are suitable materials for further planned practical application at welding process. The success of Zr-based bulk metallic glasses production in form of plate with obtained sizes is important for future progress in joining research of this group of materials.