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The wetting, reactivity, and phase formation at the liquid Ni-Al/TiB2 ceramic interfaces have been investigated at the temperatures close to the Ni-Al liquidus line. The wetting kinetics has been studied by the sessile drop technique utilizing liquid drop dispension and high-speed high-resolution video imaging. It is established that the wetting behavior changes from a nonreactive for the Al-rich melts to a dissolution-reactive for the Ni-rich melts. For the Ni concentration ≥40 at.%, TiB2 precipitates are found in the solidified Ni-Al droplets after the high-temperature interaction of the melts with TiB2 substrates. Besides, new (Al,Ti)Ni3 and (Al,Ti)2Ni21B6 phases are formed due to dissolution of TiB2 ceramic in Ni-rich melts and subsequent solidification. [ABSTRACT FROM AUTHOR]

Crystallization of Cu 47.5 Zr 48 Al 4 Co 0.5 metallic glass upon isokinetic and isothermal annealing is studied by conventional and ultrafast differential scanning calorimetry, resistive flash-annealing, and in situ high-energy X-ray diffraction. The fast-heating experiments of Cu 47.5 Zr 48 Al 4 Co 0.5 metallic glass are complemented by in situ high-energy XRD studies of the undercooled liquid by using electromagnetic levitation. The combination of complementary techniques reveals a competition between the Cu 10 Zr 7 , B2 CuZr and τ 4 Cu 2 ZrAl phases crystallization depending on heating rate and shows the specific role of Co alloying. A continuous-heating-transformation diagram for a heating rate exceeding six orders of magnitude, Φ = 0.0833 − 90 000 K s−1, and a time-temperature-transformation diagram are constructed. [Display omitted] [ABSTRACT FROM AUTHOR]

The wettability of glassy, microcrystalline and nanocrystalline carbon materials by liquid sulfur is studied by the sessile-drop technique applying the contact heating and drop-dispension procedures. Liquid sulfur shows a good wetting on all examined substrates just after melting, although the contact angle depends on the type and structure of the carbon material. Sulfur drops remain on the surfaces of glassy carbon and electrographite, whereas the liquid infiltrates into the substrates pressed from carbon micro- or nanoparticles. In the latter case, the infiltration rate increases along with decreasing size of particles used for preparation of the substrates, indicating a role of capillarity. The wetting and adhesion in the sulfur-carbon material systems are determined by the van der Waals interactions. [ABSTRACT FROM AUTHOR]

It is shown that ZrO2 nanoparticles essentially stimulate the heterogeneous nucleation of droplets from the minority phase in Al-Pb monotectic alloys, which results in a significant increase of the number of Pb particles and in a decrease of their size upon solidification. This is related to the contact angle between coexisting liquid phases and ZrO2 ceramic, which is 20-30 degrees in the Al35Pb65 alloy and 35-40 degrees in the Al29.4In70.6 alloy. In the Al34.5Bi65.5 alloy at 670°C, the contact angle at the (l-l) interface and ZrO2 ceramics shows a hysteresis between 37° and 115°. The contact angle between coexisting liquid phases and Al2O3 ceramic is close to zero in the Al34.5Bi65.5 alloy. [ABSTRACT FROM AUTHOR]

Co 61 Ta 6 B 33 , Co 59 Ta 8 B 33 , Co 57 Ta 10 B 33 and Co 53 Ta 10 B 37 bulk metallic glasses (BMGs) exhibit a good combination of the ultra-high fracture strength in the range of about 5.4–6.2 GPa, Vickers hardness of 1459–1653 HV0.2 and plastic strain of 0.3–3.2%, depending on composition. Glass forming-ability and physical properties of Co–Ta–B BMGs are discussed in relationship to the Ta and B content and atomic structure. Crystallization upon isochronal and isothermal annealing is studied using differential scanning calorimetry and X-ray diffraction. A novel crystalline phase with ~Ta 2 Co 15 B 8 or ~TaCo 7 B 4 formula is shown to form upon glass annealing. The incubation time for isothermal crystallization in the supercooled liquid state near T g is supposed to be sufficient for thermoplastic forming of Co–Ta–B BMGs. ga1 • Co–Ta–B BMGs with ultrahigh strength and ductility in compression tests. • High glass transition temperature and large supercooled liquid region. • Incubation time for crystallization sufficient for thermoplastic forming. • Novel boride with ~Ta 2 Co 15 B 8 or ~TaCo 7 B 4 unit formula found. [ABSTRACT FROM AUTHOR]

Metallic glasses exhibit unique mechanical properties. For metallic glass composites (MGC), composed of dispersed nanocrystalline phases in an amorphous matrix, these properties can be enhanced or deteriorated depending on the volume fraction and size distribution of the crystalline phases. Understanding the evolution of crystalline phases during devitrification of bulk metallic glasses upon heating is key to realizing the production of these composites. Here, results are presented from a combination of in situ small‐ and wide‐angle X‐ray scattering (SAXS and WAXS) measurements during heating of Zr‐based metallic glass samples at rates ranging from 102 to 104 Ks−1 with a time resolution of 4ms. By combining a detailed analysis of scattering experiments with numerical simulations, for the first time, it is shown how the amount of oxygen impurities in the samples influences the early stages of devitrification and changes the dominant nucleation mechanism from homogeneous to heterogeneous. During melting, the oxygen rich phase becomes the dominant crystalline phase whereas the main phases dissolve. The approach used in this study is well suited for investigation of rapid phase evolution during devitrification, which is important for the development of MGC. [ABSTRACT FROM AUTHOR]

The structural evolution of Co40Fe22Ta8B30 glassy particles has been studied by in-situ high-energy synchrotron X-ray diffraction (XRD) upon isochronal annealing. The changes in position, intensity, and full width at half maximum (FWHM) of the first and second diffuse maxima of the XRD patterns suggest the occurrence of irreversible structural relaxation upon the first heating up to a temperature close to the glass transition temperature Tg. The variations in reduced pair correlation functions upon annealing are discussed in the frame of the topological fluctuation theory for structural relaxation. Isochronal annealing of the Co40Fe22Ta8B30 glassy particles improves their soft magnetic properties through decreasing the coercivity and increasing the magnetic susceptibility, saturation magnetization, and Curie temperature. [ABSTRACT FROM AUTHOR]

A combination of conventional calorimetry, ultra-fast scanning calorimetry and resistive heating gives access to heating rates exceeding 6 orders of magnitude allowing to probe crystallization kinetics and mechanisms in a Cu-Zr-Al metallic glass. Continuous-heating-transformation and double-peak time-temperature-transformation diagrams are constructed and related to the formation of glass–crystal composites with enhanced ductility. The metastable B2-CuZr phase becomes dominantly formed at a heating rate of ~102 K s−1 and higher. A critical heating rate to bypass crystallization is ~10,000 K s−1. For isothermal annealing at >850 K, only one crystallization event is detected; for lower temperatures, a complex two-step transformation occurs. Image, graphical abstract [ABSTRACT FROM AUTHOR]

Additively manufactured metallic materials typically exhibit preferential <001> or <110> crystallographic orientations along the build direction. Nowadays, the challenge is to program crystallographic orientation along arbitrary 3D direction in additive‐manufactured materials. In this work, it is established a technique of multitrack coupled directional solidification (MTCDS) to program the <001> crystallographic orientation along an arbitrary 3D direction in biomedical beta‐type Ti‐Nb‐Zr‐Ta alloys via laser powder bed fusion (LPBF). MTCDS can be achieved via directional solidification of coupled multi‐track melt pools with a specific temperature gradient direction. This results in continuous epitaxial growth of the β‐Ti phase and consequently sets the <001> crystallographic orientation along an arbitrary 3D direction. This way, relatively low elastic modulus values of approximately 60 ± 1.2 GPa are customized along an arbitrary 3D direction. It is expected that MTCDS can be generalized to a wide range of applications for programming specific crystallographic orientations and, respectively, tailoring desired properties of different metallic materials. [ABSTRACT FROM AUTHOR]

Abstract The impact of minor additions of Ni nanoparticles on the dynamic viscosity of the liquid Sn-3.0Ag-0.5Cu alloy (SAC305; in wt%) is examined. The nanocomposite samples were prepared from commercial SAC305 powder and Ni nanopowder by cold pressing. The dynamic viscosity of the (Sn 96.5 Ag 3.0 Cu 0.5) 100–x Ni x alloys measured during heating and cooling exhibited a hysteresis in a temperature range up to 100 K above the melting temperature. This is supposed to be related to the structural transformations caused by dissolution of Ni nanoparticles in the liquid Sn-based matrix upon heating. The experimental values of the viscosity of the (Sn 96.5 Ag 3.0 Cu 0.5) 100–x Ni x alloys are in a good agreement with calculated data using thermodynamic approaches. Highlights • The viscosity of liquid SAC305 alloy with additions of Ni nanoparticles was measured. • The viscosity of liquid SAC305 alloys increases with increasing content of nano Ni. • The viscosity of liquid (SAC305) 100−x Ni x alloys was predicted by thermodynamic models. [ABSTRACT FROM AUTHOR]

The relationship between the excess volume and the structure of Fe–Cr–Ni melts is investigated using containerless levitation and in situ high-energy synchrotron x-ray diffraction techniques. The density of six hypoeutectic Fe–Cr–Ni alloys along the 72 wt. % Fe isopleth was measured in the stable and undercooled regions, and the excess volume was evaluated as a function of Cr concentration. It is found that the 72Fe–Cr–Ni alloys exhibit a positive sign of excess volume and the amount increases with increasing Cr concentration. Analysis of the structure factor and pair distribution function of the alloy family reveals that the short-range order in the melt becomes more pronounced with decreasing Cr concentration; this demonstrates a direct correlation between the excess volume and local liquid structure. A characteristic signature of the icosahedral structure is observed in the structure factor of the melts, and the potential origin of the positive excess volume of the 72Fe–Cr–Ni alloys is qualitatively discussed in relation to the icosahedral structure. [ABSTRACT FROM AUTHOR]

To understand the effect of aluminum addition on the non-equilibrium solidification of the equiatomic CoCrFeNi alloy, the Al 0.3 CoCrFeNi and AlCoCrFeNi high-entropy alloys (HEAs) have been investigated in situ using electromagnetic levitation and high-energy synchrotron X-ray diffraction (XRD). Because the five-component alloys could not be deeply undercooled, the studies were confined to the low undercooling regime. The in situ XRD revealed that a fcc single-phase solid solution is the primary crystalline phase nucleating in Al 0.3 CoCrFeNi melt undercooled up to 80 K. In contrast, the B2 ordered phase appears as the primary phase in the AlCoCrFeNi melt, at least at a low undercooling of about 30 K. These results correlate with the equilibrium phase diagrams available. Crystal growth velocities of the Al 0.3 CoCrFeNi alloy are shown to be smaller than for CrFeNi and CoCrNi equiatomic alloys; nonetheless, they are in the same order of magnitude. Spontaneous grain refinement was observed in the Al 0.3 CoCrFeNi alloy solidified at a low undercooling of Δ T = 70 K. [Display omitted] • In situ non-equilibrium solidification of high-entropy alloys is studied. • Al 0.3 CoCrFeNi alloy shows a sluggish crystal growth, compared to CoCrFeNi. • Spontaneous grain refinement is observed as undercooling of the Al 0.3 CoCrFeNi melt increases. • AlCoCrFeNi forms B2 phase at high temperature and bcc and B2 at room temperature. [ABSTRACT FROM AUTHOR]

Chalcogenide phase‐change materials combine a remarkable set of properties that makes them promising candidates for future non‐volatile memory applications. Binary data storage exploits the high contrast in electrical and optical properties between the covalent amorphous and metavalent crystalline phase. Here the authors perform an analysis of the liquid phase kinetics of the phase‐change material Ge3Sb6Te5, which is the key to ultrafast switching speeds. By employing four experimental techniques, the viscosity is measured over sixteen orders of magnitude despite its propensity for fast crystallization. These measurements reveal that the liquid undergoes a transition in viscosity–temperature dependence associated with a liquid–liquid phase transition. The system exhibits a shallow viscosity change with temperature near the glass transition which stabilizes the memory cells in the amorphous state and which limits the severity of relaxation processes. Meanwhile, when heated during the writing process, the fragility increases to more than double, causing the viscosity to drop rapidly enabling a nanosecond crystallization speed. This change in viscosity–temperature dependence is highly unusual among glass forming liquids and is reminiscent of the behavior of water. This viscosity transition is also key to the technological success of phase‐change materials for computer memory applications. [ABSTRACT FROM AUTHOR]

Despite recent progress in understanding the outstanding role of shear bands in plastic deformation of metallic glasses, the details of structural changes in the shear-induced zone is not yet known. In order to probe such changes, we determined the distribution of residual strains at short- and medium-range order around a single shear band in cold-rolled Vit105 bulk metallic glass using a nano-focused high energy X-ray beam. Plastic deformation results in significant residual normal and shear strains at distances of more than 15 μm around the shear band. Based on a detailed analysis of the distribution profile, the magnitude and the direction of the residual shear strain, it is suggested that the shear strain plays a dominant role, compared to the normal strains, for triggering nucleation of further shear bands from a mature shear band. [ABSTRACT FROM AUTHOR]

Fully amorphous rods with diameters up to 2 mm diameter were obtained upon 0.5 at.% Cu addition to the Fe 36 Co 36 B 19.2 Si 4.8 Nb 4 bulk metallic glass. The Cu-added glass shows a very good thermal stability but, in comparison with the Cu-free base alloy, the entire crystallization behavior is drastically changed. Upon heating, the glassy (Fe 36 Co 36 B 19.2 Si 4.8 Nb 4 ) 99.5 Cu 0.5 samples show two glass transitions-like events, separated by an interval of more than 100 K, in between which a bcc-(Fe,Co) solid solution is formed. The soft magnetic properties are preserved upon Cu-addition and the samples show a saturation magnetization of 1.1 T combined with less than 2 A/m coercivity. The relaxation behavior prior to crystallization, as well as the crystallization behavior, were studied by time-resolved X-ray diffraction using synchrotron radiation. It was found that both glassy alloys behave similar at temperatures below the glass transition. Irreversible structural transformations take place when approaching the glass transition and in the supercooled liquid region. [ABSTRACT FROM AUTHOR]

[Display omitted] The complex phase evolution sequence of a promising new high temperature structural alloy with composition Al 20 Cr 20 Fe 35 Ni 20 Ti 5 (at.%) has been studied in situ using an electromagnetic levitation (EML) setup combined with time-resolved high energy X-ray diffraction (XRD), as well by scanning transmission electron microscopy (STEM) observations during in situ heating. These experiments were supplemented by both scanning electron microscopy (SEM) and high resolution STEM observations of the as-cast alloy microstructure, as well as by energy dispersive X-ray spectroscopy (EDS) composition measurements. Differential scanning calorimetry (DSC) was used to identify liquidus, solidus, A2 ↔ B2, and B2 ↔ L2 1 transition temperatures. The results obtained by these complementary techniques indicate that the alloy forms primary dendrites of A2-structured body-centered cubic (bcc) phase initially from the melt, followed by ordered bcc of B2-structure in interdendritic regions once compositional segregation has sufficiently enriched the remaining liquid. Ordered B2 precipitates form within the primary A2-structured dendrites and the interdendritic B2 regions undergo a continuous decomposition reaction into a maze-like arrangement of A2 and B2/L2 1 phases below the solidus. Below approximately 1380 K, the B2 domains in both dendritic and interdendritic regions likely undergo a continuous ordering transition to the L2 1 phase. The experimental observations of Al 20 Cr 20 Fe 35 Ni 20 Ti 5 are found to be in good agreement with CALPHAD predictions but suggest that the solubility limits of the L2 1 -Heusler phase in the database should be relaxed to include greater Fe solubility for the Ni sublattice and to consider deviations in order parameter from stoichiometric ordering. [ABSTRACT FROM AUTHOR]

Development of the two-phase bulk metallic glasses (BMGs) is essentially retarded due to difficulties in finding of phase-separated (immiscible) alloys with high glass-forming ability (GFA) of coexistent phases. Referring to the concept of solute partitioning and minimization of free energy, in this work we present an idea that a metallic liquid system containing two liquids with individual self-assembled eutectic composition may yield two-phase BMGs upon casting. The formation of the two-glass structure is discussed and a strategy of partial substitution of chemically similar elements for overcoming the drawback of low GFA is proposed. A family of two-phase zirconium–lanthanide based metallic glasses in bulk form is developed. The mechanical behavior of the two-phase BMGs with different ratio of zirconium-rich to lanthanide-rich glassy phase is studied for the first time. This work provides a new concept for fabrication of two-phase BMGs and reveals the role of constituent phases in determining the mechanical properties of the whole glass. [ABSTRACT FROM AUTHOR]

The martensitic transformation within B2 phase plays a critical role for the ductility of CuZr-based bulk metallic glass (BMG) composites, yet the underlying mechanism for the martensitic transformation process needs further investigations. Here, we found that the onset temperature of the thermally-activated martensitic transformation for CuZr-based BMG composites was reduced to 162.7 ± 2.5 K, which is far lower than those of polycrystalline samples, due to the stabilization of the austenitic phase induced by crystalline-amorphous interfaces. In situ high-energy X-ray diffraction measurements (HEXRD) further demonstrate that the thermally-activated martensitic transformation is governed by an extremely incomplete martensitic transformation from B2 to B19' and B33 phases without the decomposition of B2 phase which generally appears in polycrystalline samples. Due to unconfined stress states during the thermally-activated martensitic transformation, B33 phase forms more early during thermal process than deformation process. The present study provides a further understanding on the martensitic transformation behaviors of shape memory type CuZr-based BMG composites. Image 1 • In situ observations on thermally-activated martensitic transformation for BMG composites was conducted. • Martensitic transformation temperature is far below room temperature. • Extremely incomplete martensitic transformation was observed. • Decomposition of B2 phase does not appear during martensitic transformation. • B33 phase forms earlier during thermal process than deformation process. [ABSTRACT FROM AUTHOR]

By adding 0.5 at. % Cu to the strong but brittle [(Fe0.5Co0.5)0.75Si0.5B0.20]96Nb4 bulk metallic glass, fully amorphous rods with diameters up to 2mm were obtained. The monolithic samples with 1mm diameter revealed a fracture strain of 3.80% and a maximum stress of 4143 MPa upon compression, together with a slight work-hardening behavior. SEM micrographs of fractured samples did neither reveal any shear bands on the lateral surface nor the typical vein patterns which characterize ductile fracture. However, some layers appear to have flowed and this phenomenon took place before the brittle final fracture. An estimate of the temperature rise ΔT in the shear plane gives 1039 K, which is large enough to melt a layer of 120 nm. The overall performance and the macroscopic plastic strain depend on the interaction between cleavage-like and viscous flow-like features. Mechanical tests performed in-situ under synchrotron radiation allowed the calculation of the strain tensor components, using the reciprocal-space data and analyzing the shift of the first (the main) and the second broad peak positions in the X-ray diffraction patterns. The results revealed that each atomic shell may have a different stiffness, which may explain the macroscopic compressive plastic deformation. Also, there were no signs of (nano) crystallization induced by the applied stress, but the samples preserve a monolithic amorphous structure until catastrophic failure occurs. [ABSTRACT FROM AUTHOR]

Flash Joule-heating was applied to the Cu47.5Zr47.5Al5 metallic glass for designing fully crystalline metastable nanocomposites consisting of the metastable B2 CuZr and low-temperature equilibrium Cu10Zr7 phases. The onset of crystallization was in situ controlled by monitoring resistivity changes in the samples. The effect of heating rate and annealing time on the volume fraction of the crystalline phases and mechanical properties of the nanocomposites was studied in detail. Particularly, an increase of the heating rate and a decrease of the annealing time lead to a lower number of equilibrium Cu10Zr7 precipitates and an increase of tensile ductility. Tailoring of these non-equilibrium microstructures and mechanical properties may not be possible unless one starts with a fully glassy material that opens new perspectives for designing metastable nanomaterials with unique physical properties. [ABSTRACT FROM AUTHOR]

Details of fast-resistive-heating setups, controlled heating ranging from ∼101 K s−1 to ∼103 K s−1, to study in situ phase transformations (on heating and on cooling) in metallic glasses by high-energy synchrotron x-ray diffraction are discussed. Both setups were designed and custom built at the Leibniz Institute for Solid State and Materials Research Dresden (IFW Dresden) and have been implemented at the P02.1 Powder Diffraction and Total Scattering Beamline and the P21.1 Swedish Materials Science Beamline at PETRA III storage ring, DESY, Hamburg. The devices are interchangeable at both beamlines. Joule heating is triggered automatically and is timed with the incident beam and detector. The crystallization process can be controlled via a feedback circuit by monitoring the change in the time-dependent resistivity and temperature of glasses. Different ambient atmospheres, such as vacuum and inert gases (He and Ar), can be used to control oxidation and cooling. The main focus of these devices is on understanding the crystallization mechanism and kinetics in metallic glasses, which are brittle and for which fast heating gives defined glass–crystal composites with enhanced plasticity. As an example, phase-transformation sequence(s) in a prototyped Cu–Zr-based metallic glass is described on heating, and a crystalline phase beneficial to the plasticity is identified. [ABSTRACT FROM AUTHOR]

Solidification and growth behavior of undercooled eutectic CoSi–CoSi 2 melts was observed using containerless levitation and in situ high-energy synchrotron X-ray diffraction techniques. Three metastable solidification pathways of eutectic CoSi–CoSi 2 were determined as a function of undercooling. Upon double recalescence at low undercoolings the primary and secondary phases are CoSi and CoSi 2 , while at high undercoolings the phase formation sequence is reversed. At intermediate undercoolings a single recalescence was observed and attributed to a crossover of the nucleation barriers for the two phases. Scanning electron microscopy combined with electron back-scattering diffraction measurements revealed changes of the morphological characteristics and orientation of CoSi and CoSi 2 phases for different solidification pathways. Image 1 [ABSTRACT FROM AUTHOR]

Programming Crystallographic Orientation in Additive-Manufactured Beta-Type Titanium Alloy (Adv. Sci. 28/2023) It is expected that MTCDS can be generalized to a wide range of applications where specific crystallographic orientation at defined locations/region of a component is needed, especially for medical load-bearing bone implants with microstructure-controlled and locally variable elastic modulus for optimal stress shielding reduction. B Crystallographic Orientation b In article number 2302884, Xuan Luo, Annett Gebert, Yuanyuan Li, Chao Yang, and co-workers establish a technique of multi-track coupled directional solidification (MTCDS) to program the <001> crystallographic orientation along an arbitrary 3D direction in biomedical beta-type alloys via laser powder bed fusion. [Extracted from the article]

A density variation in shear bands visible by electron microscopy is correlated with compositionally altered locations measured by atom-probe tomography in plastically-deformed Al 85.6 Y 7.5 Fe 5.8 metallic-glass ribbons. Two compositionally distinct regions are identified along shear bands, one is Al-rich (~92 at.%), the other is Al-depleted (~82.5 at.%) and both regions show marginal concentration fluctuations of Y and Fe. The elemental re-distribution is observed within shear bands only, and no chemical exchange with the surrounding glassy matrix is observed. Unlabelled Image [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • Self-organized hierarchical separation. • Liquid-liquid phase separation in super-gravity field. • Efficient recycling of overall metals in WPCBs. • Green strategy for the treatment of toxic heavy metals. Abstract Waste electrical and electronic equipment is rapidly increasing worldwide, resulting in a large quantity of waste printed circuit boards (WPCBs). There is a great challenge on how to efficiently separate mixed metals in WPCBs, which consists of more than 10 elements including hazardous Cr, Pb and Cd. In this work, based on atomic interactions, a method of liquid-liquid hierarchical separation is developed to separate the mixed metals dissociated from the pyrolyzed WPCBs of mobile phones. The hierarchical separation of L→L Fe-rich + L Cu,Pb-rich , L Cu,Pb-rich →L Cu-rich + L Pb-rich and L Pb-rich →S Cu-dendritical + L' Pb-rich produces four immiscible Fe-rich, Cu-rich, Cu-dendritical and Pb-rich substances. The separation rate between these substances can reach more than 96% in a super-gravity field of G = 1000 g. Other metals selectively distribute in the four substances. The Fe-rich substance collects Cr, Co, Ni and Si. Almost all of Au and Ag are trapped in the Cu-rich and Cu-dendritical substances. The low-melting-point metals, i.e. Bi, Cd, In and Sn, are located in the Pb-rich substance. This work provides a green shortcut for efficiently separating and recycling overall metals in WPCBs. [ABSTRACT FROM AUTHOR]

Abstract The structure of Ge x Te 100- x (x = 14.5, 18.7, 23.6) glasses prepared by twin roller quenching technique was investigated by neutron diffraction, X-ray diffraction and Ge-K-edge X-ray absorption spectroscopy measurements. Large scale structural models were obtained for each composition by fitting the experimental datasets in the framework of the reverse Monte Carlo technique. It was found that the majority of Ge and Te atoms satisfy the 8-N rule. Simulation results indicate that Ge-Ge bonding is not significant for x = 14.5 and 18.7. The shape and position of the first peak of the Ge-Ge partial pair correlation function evidence the presence of corner sharing tetrahedra already in compositions (x = 14.5 and 18.7) where 'sharing' of a Te atom by two Ge atoms could be avoided due to the low concentration of Ge. Graphical abstract Image 1 Highlights • The average coordination numbers of Ge and Te are close to 4 and 2, respectively. • Corner sharing tetrahedra can be found already in Ge14.5Te85.5. • No Ge-Ge bonds are found during the fitting of diffraction and EXAFS data of Ge14.5Te85.5 and Ge18.7Te81.3. [ABSTRACT FROM AUTHOR]

The crystallization mechanism and solid-state phase transformations in Cu 46.5 Zr 48 Al 4 Nb 1.5 metallic glass upon isokinetic and isothermal annealing are studied by using conventional and fast-scanning differential calorimetry, electric current flash-annealing, electromagnetic levitation, and in-situ high-energy synchrotron X-ray diffraction. Continuous-heating-transformation and time-temperature-transformation diagrams mapping the formation and evolution of the Cu 10 Zr 7 , B2 CuZr, τ 3 Zr 51 Cu 28 Al 21 and τ 4 Cu 2 ZrAl phases in dependence on heating rate and temperature are constructed. Cu 46.5 Zr 48 Al 4 Nb 1.5 metallic glass shows an increased propensity for the Cu 10 Zr 7 phase formation compared to the parent Cu 47.5 Zr 47.5 Al 5 glass. • Crystallization of Cu 46.5 Zr 48 Al 4 Nb 1.5 metallic glass upon flash-annealing is studied. • Processing parameters for fabrication of glass-matrix composites are established. • Nb-microalloying enhances formation of Cu 10 Zr 7 phase upon annealing. • B2 CuZr is always primary phase by crystallization from undercooled liquid. [ABSTRACT FROM AUTHOR]

The constituent ratio merged into as-fabricated composites can directly influence the content of in-situ formed reinforcing phases, which is closely related to the mechanical performance of these composites. In this work, aluminum matrix composites reinforced with 10, 15, and 20 wt% (ZrC+TiC) ceramic fractions have been manufactured by laser powder bed fusion (LPBF) additive manufacturing. The effect of hybrid ceramic reinforcement content on laser absorption behavior, fabrication and fraction of micro-nanoscale reinforcing phases, mechanical performance of the as-fabricated aluminum matrix composites is studied. In the laser processing, TiC reacts with ZrC to synthesize interfacial layer on the unmolten ceramic particals and precipitate nano-particles. With the hybrid ceramic content raising from 10 to 20 wt%, the laser absorption behavior is enhanced, and the nano-particle fraction increases. The micro/nano hardness of the composites with 20 wt% ceramic content, reaches 120 HV 0.2 and 1.33 GPa, respectively. An elastic modulus of ∼94.4 GPa and tensile strength of ∼280 MPa are obtained for the 15 wt% (ZrC+TiC)/Al composites, much higher than those of the unreinforced Al matrix. This is attributed to the combination of formation of nano-precipitates and coherent bonding at the reinforcement/matrix interfaces in these composites. • (ZrC+TiC)/Al composites with different ceramic contents are fabricated by LPBF. • Spherical and acicular nano-reinforcements in-situ precipitate in the matrix. • A thin transition layer is formed at the unmelted ceramic/matrix interface. • The strengthening mechanism of the (ZrC+TiC)/Al composites is revealed. [ABSTRACT FROM AUTHOR]

Short range order in glassy 0.9(Ge 0.1 As 0.15 Te 0.75 )–0.1Cu (GATC1) and 0.9(Ge 0.05 As 0.55 Te 0.4 )–0.1Cu (GATC2) was studied by neutron- and X-ray diffraction as well as EXAFS (extended X-ray absorption fine structure) measurements at the K-edges of all components. The reverse Monte Carlo simulation technique was used to create models consistent with all experimental datasets. It was found that Cu binds predominantly to Te in GATC1 while Cu–As and Cu–Cu bonding is also significant in GATC2. Ge and As atoms have 4 and 3 Ge/As/Te neighbors in both compositions. In GATC1 the formation of ‘extra’ Te–Te bonds can be observed, similarly to GeTe 4 –AgI glasses. [ABSTRACT FROM AUTHOR]

The structure of (GeTe4)1-x(AgI)x (x = 0.15 and 0.25) glasses has been investigated by X-ray and neutron diffraction as well as extended X-ray absorption spectroscopy (EXAFS) and Raman spectroscopy. Large-scale structural models have been obtained by fitting simultaneously the experimental datasets in the framework of the reverse Monte Carlo simulation technique (RMC). Short-range order parameters have been calculated and compared with that of GeTe4. Doping with AgI affects the structure of the host GeTe4 matrix in two ways. First, while Te is essentially twofold coordinated in GeTe4, its coordination number is as high as ~2.9 ± 0.3 for x = 0.25. The change is mainly due to the increased fraction of Te-Te bonds. Second, Ge atoms remain fourfold coordinated but the tetrahedral symmetry is distorted due to the elongation of some Ge-Te bonds. The incorporation of AgI in the GeTe4-based host covalent matrix and the Te coordination increase explains the enhanced thermal stability of (GeTe4)1-x(AgI)x in the supercooled liquid-state hindering the crystallization of Te found in case of GeTe4 glass. [ABSTRACT FROM AUTHOR]

Abstract: The influence of ball milling on the atomic structure and magnetic properties of the Co40Fe22Ta8B30 metallic glass with a high thermal stability and excellent soft magnetic properties has been investigated. After 14h of milling, the obtained powders were found to consist mainly of an amorphous phase and a small fraction of the (Co,Fe)21Ta2B6 nanocrystals. The changes in the reduced pair correlation functions suggest noticeable changes in the atomic structure of the amorphous upon ball milling. Furthermore, it has been shown that milling is accompanied by introduction of compressive and dilatational sites in the glassy phase and increasing the fluctuation of the atomic-level hydrostatic stress without affecting the coordination number of the nearest neighbors. Ball milling has decreased the thermal stability and significantly affected the magnetic properties through increasing the saturation magnetization, Curie temperature of the amorphous phase and coercivity. [Copyright &y& Elsevier]

The structure of Te-rich (75-80 at.% Te) and Te-poor (40 at.% Te) Ge-As-Te glasses has been investigated by diffraction and extended X-ray absorption fine structure ( EXAFS) measurements. Large-scale structural models have been created by fitting simultaneously diffraction and EXAFS datasets by the reverse Monte Carlo simulation technique. It is found that As-As bonds improve the fit quality in the case of Te-rich glasses while no Ge-Ge bonding is necessary in these compositions. In the Te-poor glasses, Te-Te homopolar bonds are also observed while Ge binds preferentially to Te rather than to As. Ge-As and Ge-Te coordination numbers do not change significantly with increasing Ge content. [ABSTRACT FROM AUTHOR]

Time- and temperature-resolved phase formation in the equiatomic NbTiVZr refractory high-entropy alloy has been studied in situ using high-energy synchrotron X-ray diffraction and high-speed video imaging during non-equilibrium solidification. Phase formation is shown to be dependent on the solidification conditions. When the melt is undercooled over 80 K it crystallizes as a bcc single-phase solid solution despite solute partitioning between dendrites and interdendritic regions. When the sample is for some time kept in the semisolid state, two additional bcc phases form in the interdendritic regions. The crystal growth velocity for the NbTiVZr alloy, as estimated from the high-speed videos, shows pronounced sluggish kinetics. [Display omitted] [ABSTRACT FROM AUTHOR]

Abstract: In this letter we report about a new melt-spun Co40Fe22Ta8B30 metallic glass with a wide supercooled liquid region of 74K. X-ray diffraction (XRD) and high resolution transmission electron microscopy (HRTEM) investigations confirmed that crystallization occurs with significantly longer incubation time during annealing above the glass transition, as compared to the well-known Co43Fe20Ta5.5B31.5 glassy alloy. The new alloy as a good soft magnetic material showed a very low coercivity of 0.8A/m and polarization of 0.5T. The origin of high thermal stability was attributed to the formation of Ta–Ta bonds in the microstructure and the absence or very low quantity of Ta-based units with the composition close to the stoichiometry of the (Co,Fe)21Ta2B6 crystalline phase. [Copyright &y& Elsevier]

The solidification behavior of the CoCrFeNi high-entropy alloy and the ternary CrFeNi and CoCrNi medium-entropy suballoys has been studied in situ using high-speed video and synchrotron X-ray diffraction on electromagnetically levitated samples. In all alloys, the formation of a primary metastable bcc phase was observed if the melt was sufficiently undercooled. The delay time for the onset of the nucleation of the stable fcc phase, occurring within bcc crystals, is inversely proportional to the melt undercooling. The experimental findings are corroborated by thermodynamic calculations of stable and metastable phase diagrams for the (CoCrNi)-Fe section. Crystal-growth velocities for the CrFeNi, CoCrNi, and CoCrFeNi medium- and high-entropy alloys extracted from the high-speed video sequences in the present study are comparable to the literature data for Fe-rich Fe-Ni and Fe-Cr-Ni alloys, evidencing the same crystallization kinetics. The effect of melt undercooling on the microstructure of solidified samples is analyzed and discussed. [Display omitted] [ABSTRACT FROM AUTHOR]

Image, graphical abstract The relationship between remelting and undercooling in Co 38.2 Si 61.8 (at. %) eutectic alloys is investigated with in situ X-ray diffraction experiments and microstructural observations. High-energy in situ X-ray diffraction during uncoupled eutectic solidification of undercooled Co 38.2 Si 61.8 allows the phase fractions to be tracked through time and reveals remelting of primary solid coincident with the formation of secondary solid. Microstructure analysis suggests that remelting occurs at the supersaturated dendrite interior. The remelted solid fraction is quantified for a wide range of solidification conditions and found to be strongly correlated with the secondary undercooling of the melt, yet independent of convection and containerless processing technique. A remelting limit was observed in experiments with primary CoSi 2 , indicating that system-specific factors impose additional constraints. [ABSTRACT FROM AUTHOR]

High-entropy alloys (HEAs) have inspired considerable interest due to their attractive physical and mechanical properties. In this work, the microstructural evolution induced by different heat treatments on rapidly solidified hypoeutectic precursors of a Fe26.7Co26.7Ni26.7Si8.9B11 HEA is investigated and correlated with the corresponding mechanical properties. The microstructures of the rapidly solidified precursors are composed of primary fcc solid solution dendrites embedded in a eutectic matrix. When the samples are annealed at different temperatures after furnace cooling or quenching, respectively, the eutectic structure gradually decomposes into fcc, tetragonal (Fe,Co)2B, and hexagonal Ni31Si12 crystals with increasing annealing temperature, leading to a gradual increase of the content of the fcc crystals and both their aggregation and coarsening. Then the dominant structural framework gradually transforms from eutectic structures to fcc dendrites and ultimately the (Fe,Co)2B crystals become isolated as dominant reinforcement particles distributed in the interdendritic regions. This gradual microstructural transition from hypoeutectic to quasi-duplex structures leads to the change of the dominant deformation mechanism from crack-controlled to dislocation-dominated deformation, which allows to control both ductility and strength in a wide range. Hence, this study provides some guideline for how to tune the microstructure and mechanical properties of HEAs. [ABSTRACT FROM AUTHOR]

GeTe is a prototypical phase-change material employed in data storage devices. In this work, the atomic structure of liquid GeTe is studied by x-ray and neutron diffraction in the temperature range from 1197 to 998 K. The dynamic viscosity is measured from 1273 to 953 K, which is 55 K below the solidification point, using an oscillating-cup viscometer. The density of liquid GeTe between 1293 and 973 K is determined by the high-energy γ-ray attenuation method. The experiments are complemented with ab initio molecular dynamics (AIMD) simulations based on density functional theory (DFT). Compatibility of the AIMD-DFT models with the diffraction data is proven by simultaneous fitting of all data sets in the frame of the reverse Monte Carlo simulation technique. It is shown that octahedral order dominates in liquid GeTe, although tetrahedral structures are also present. The viscosity of the equilibrium and weakly undercooled liquid GeTe obeys the Arrhenius law with a small activation energy of the order of 0.3 eV, which is indicative of a highly fragile liquid. The calculated density of states and electronic wave functions point to the existence of a pseudogap and localized electron states within the gap in the equilibrium liquid near the melting point as well as in the undercooled liquid. [ABSTRACT FROM AUTHOR]

Recently, CuZr-based bulk metallic glass (BMG) composites reinforced by the TRIP (transformation-induced plasticity) effect have been explored in attempt to accomplish an optimal of trade-off between strength and ductility. However, the design of such BMG composites with advanced mechanical properties still remains a big challenge for materials engineering. In this work, we proposed a technique of instantaneously and locally arc-melting BMG plate to artificially induce the precipitation of B2 crystals in the glassy matrix and then to tune mechanical properties. Through adjusting local melting process parameters (i.e. input powers, local melting positions, and distances between the electrode and amorphous plate), the size, volume fraction, and distribution of B2 crystals were well tailored and the corresponding formation mechanism was clearly clarified. The resultant BMG composites exhibit large compressive plasticity and high strength together with obvious work-hardening ability. This compelling approach could be of great significance for the steady development of metastable CuZr-based alloys with excellent mechanical properties. [ABSTRACT FROM AUTHOR]