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The effect of H+‐ion irradiation on the structure and properties of a Cu50Zr50 metallic glass (MG) is investigated. High‐energy synchrotron X‐Ray diffraction results indicate that the glass maintains its amorphous nature after ion irradiation. As the ion fluence increases, the atomic bond length of MGs becomes shorter, whereas the nanohardness and Young's modulus increase from 7.08 ± 0.01 and 111.3 ± 1.1 GPa for the as‐spun sample to 8.59 ± 0.06 and 123.1 ± 1.3 GPa for the sample irradiated with 2 × 1016 cm−2 fluence. The corrosion potential of the studied MG in 1 mol L−1 HCl increases from −0.5953 to −0.4519 V, suggesting an enhanced corrosion resistance of MGs after ion irradiation. The modification of mechanical properties and corrosion resistance can be interpreted from the ion irradiation‐induced structural evolution. The results obtained herein can be beneficial for better understanding the mechanical properties and corrosive behaviors of MGs under extreme conditions like ion irradiation, thus promoting their industrial applications. [ABSTRACT FROM AUTHOR]

In metallic glass composites (MGCs), the existence of crystalline phases causes the structures of amorphous matrix to become relatively heterogeneous near the crystalline phase, resulting in the difference of mechanical properties in micro- or nano-scale in amorphous matrix near crystalline/matrix interface. In this study, this difference was characterized by nanoindentation technology, and the pile-up height was quantitatively related to the activation volume of shear transformation zones (STZs). Molecular dynamics simulations were conducted to investigate the activation behaviors of STZs during nanoindentation process of amorphous matrix. The influences of crystalline phase on deformation behaviors of amorphous matrix near the interface in MGCs were analyzed in details. • For the interface area of MGCs, the hardnesses of interface, crystalline phase and amorphous matrix increase in turn. • The existence of crystalline phase will cause the gradient distribution of free volume away from the interface in amorphous matrix. • The relationship between the pile-up height of nanoindentation in amorphous matrix, the free volume content and the number of STZs is established. [ABSTRACT FROM AUTHOR]

It has been well documented that the maximum thickness of as-cast glassy samples attainable through conventional metallurgical routes is the decisive criteria for measuring the glass-forming ability (GFA) of bulk metallic glasses (BMGs). Here we report the exceptionally high GFA of an FeCoCrMoCBY alloy which can be fabricated in the form of glassy rods with a maximum sample thickness of at least 16 mm. It is demonstrated that, by substituting Fe with a proper amount of Co in a previously reported Fe-based BMG alloy, the glass formation of the resultant new alloy can be extensively favored both thermodynamically and kinetically. The new ferrous BMG alloy also exhibits a high fracture strength of 3500 MPa and Vickers hardness of 1253 kg mm-2. [ABSTRACT FROM AUTHOR]

Abstract: Conventional crystalline materials usually exhibit a ductile to brittle transition behaviour at low temperatures. An increase in the strength is always accompanied by a decrease in the plasticity. Here the authors report on a significant enhancement in both compressive strength and plasticity of a Ti-based bulk metallic glass (BMG) deformed at low temperatures. The ductilization of the BMG system can be evidently attributed to the formation of dense shear bands and the rotation mechanism of shear bands. The cryogenic surroundings can effectively slow down the mobility and diffusion of the atoms and consequently, suppress the nucleation and growth of nanocrystals during the deformation process, allowing the simultaneous improvement in the mechanical responses of the glassy alloy to compressive loading far below the ambient temperature. [Copyright &y& Elsevier]

High-purity melting is critical for casting metallic glass components, which would be achieved by developing the induction skull melting (ISM) technology used in casting process. The melting process of metallic glass components during ISM is urgently desired to be understood, which is rare so far. Based on this, a full-scale coupling simulation model for ISM technology with finite element method (FEM) was proposed, which contains all physical fields engaged in the melting processes. Furthermore, the metallic glass melting process was experimentally and numerically investigated based on the full-scale coupling model. The distribution of the multi-physics field within the charge was elaborated based on the numerical simulation results, especially electromagnetic field contribution, heat transfer, meniscus shape and melt reflux zone. Furthermore, due to its high viscosity, a long holding time to improve melt homogeneity is necessary for metallic glass melt. The chief aim of this work is to understand of induction melting process for melting amorphous master alloys using induction skull melting technology and to provide a foundation for the casting method to form bulk metallic glasses. [ABSTRACT FROM AUTHOR]

In this study, the deformation behaviors of a Cu 47.5 Zr 48 Al 4 Nb 0.5 bulk metallic glass composite (BMGC) in the temperature ranging from 663 K to 763 K have been investigated using uniaxial tensile tests and high-energy X-ray diffraction. Within the supercooled liquid region (SLR), the studied BMGC exhibits superplasticity and the deformation of the studied BMGC basically involves two modes, i.e., homogeneous and inhomogeneous deformation. As the temperature increases in the SLR, the yield strength of the studied BMGC gradually decreases whereas the plastic strain increases, revealing that the amorphous phase plays a dominant role in the deformation. However, there is a significant increase in the yield strength above the crystallization temperature, which indicates that the deformation is mainly contributed by the crystalline phase. The results obtained in this manuscript provide a better understanding of the temperature dependence of deformation behaviors in BMGCs. [Display omitted] • The yield strength of the BMGC decreases with the increasing temperatures below T x. • The structural evolution of the BMGC was characterized using high energy X-ray diffraction (HE-XRD). • The amorphous phase leads the deformation behaviors of the BMGC below T x , otherwise the crystalline phase dominates. [ABSTRACT FROM AUTHOR]

Using electropulsing treatment (EPT), we proposed a method to effectively tune the free volume content and the mechanical performance of a Zr-based bulk metallic glass (BMG). No crystallization takes place but the atomic scale structure changes during EPT. Appropriate EPT parameter can facilitate the increase in the free volume content, thus tailoring the nanomechanical properties of the studied BMG. • Electropulsing treatment is employed to tune the structure and mechanical properties of a Zr-based bulk metallic glass. • Appropriate EPT parameter facilitates the increase in the free volume content. • The applied current density exerts a crucial role on the incipient plasticity. [ABSTRACT FROM AUTHOR]

Abstract Here, the compressive deformation behaviors of a CuZr-based bulk metallic glass composite (BMGC) has been studied under both unconfined and confined conditions. The threshold strain for the martensitic transformation (MT) is experimentally determined to be 0.8%, and 1.9% for the unconfined and confined compression, respectively. The complicated stress state in the confined compression postpones MT of the B2 phase, which has been verified by both experiments and molecular dynamic simulation. The yielding of the B2 phase is dominated by the uniaxial compressive stress. It is expected that the obtained results can provide more insights into the deformation mechanism of BMGCs. Graphical abstract Image 1 Highlights • The threshold strain for the martensitic transformation is quantitatively determined. • The complicated stress state in the confined compression postpones martensitic transformation. • The yielding of the B2 phase is dominated by the uniaxial compressive stress. [ABSTRACT FROM AUTHOR]

Abstract The atomic structure evolution of Gd 36 Tb 20 Co 20 Al 24 high entropy metallic glass microwire from room to cryogenic temperature has been studied by in-situ high energy synchrotron X-ray diffraction. During the cooling process, the atomic volume decreases. For short-range order, the coordination numbers of all atomic pairs increase. As the temperature decreases, bond lengths of large atom-small atom and small atom-small atom pairs keep decreasing whereas that of large atom-large atom pairs unexpectedly increases continuously. The mechanism of atomic structure evolution is proposed, which might be helpful for better understanding the low temperature magnetocaloric effect of high entropy metallic glasses. Graphical abstract Unlabelled Image [ABSTRACT FROM AUTHOR]

As a versatile and nondestructive method, laser-shock peening (LSP) has been extensively utilized to improve the mechanical properties of metallic components. Nevertheless, the underlying mechanism for the LSP-induced structure transformation remains unclear. In this study, the structure and nano-mechanical behaviors of a Ti 40 Zr 25 Ni 3 Cu 12 Be 20 bulk metallic glass (BMG) were investigated before and after LSP processing. The LSP-treated BMG sample remains its amorphous structure. As the laser-beam energy increases, there is a reduction in the local order extent of LSP-treated Ti 40 Zr 25 Ni 3 Cu 12 Be 20 BMGs samples, i.e., an increase in the free-volume contents. A higher free-volume content caused a greater shear-band density for the studied BMG samples, causing a lower nano-hardness. Besides, there exists a gradient in nano-hardness along the LSP direction inside the sample, the nano-hardness increases along the LSP direction (gradually approaching the matrix hardness). This gradient effect can be attributed to the gradual decay of the shock-wave pressure with increasing the depth. [Display omitted] • Ti-based BMG remains its amorphous structure after laser shock peening (LSP). • A higher laser beam energy causes a lower local order level, a higher free volume content, a higher pile-up quantity, and a lower nano-hardness. • LSP-treated BMG sample exhibits a gradient in nano-hardness along the LSP direction. [ABSTRACT FROM AUTHOR]

The structural evolution of CuZr-based metallic glass composite (MGC) near the crystalline/matrix interface is studied by in situ transmission electron microscope (TEM) tensile straining and molecular dynamics (MD) simulation. The crystalline phase is found to undergo plastic deformation before the amorphous phase, via recoverable martensite transformation, dislocation accumulation at the interface and local amorphization between grains. Fracture does not occur along the interphase interface, but within the crystalline phase at about half a micron from the interface and parallel to it, indicating a high strength of the interface and an elevated work hardening rate of the crystalline phase just next to the interface. MD simulations show that the amorphous phase is marginally metastable with respect to the stable B2 phase, while B19′ martensitic phase is metastable with a higher energy, thus explaining the easy mutual transformation between B2 and amorphous phase, and the rarer transformation product of B19' phase from B2 on straining. [Display omitted] [ABSTRACT FROM AUTHOR]

The bending behaviors of a Zr 55 Cu 30 Ni 5 Al 10 bulk metallic glass (BMG) samples with different notch radii are studied. The artificial notch will introduce stress concentration within the BMG sample during bending. That means, smaller notch radius leads to greater stress concentration around the notch area, and thus results in earlier failure and smoother fracture surface. Then, the sample with smaller notch radius possesses smaller fracture toughness. The relationship between the stress concentration and deformation feature has been discussed in terms of grease model. [ABSTRACT FROM AUTHOR]

Bulk metallic glass composites (BMGCs) reinforced with a B2-CuZr phase exhibit improved ductility. However, the relationship between the macroscopic plastic deformation of BMGCs and the microscopic strain evolution is still poorly understood. Here, we investigated the strain-field evolution of a Cu 44.3 Zr 48 Al 4 Nb 3.7 (at%) BMGC by using an in-situ digital image correlation technique during tensile deformation. The strain-field evolution in the composite containing B2-CuZr particles was analysed and compared to that in a Cu 47 Zr 48 Al 4 Nb 1 BMG. We found that a high degree of shear strain heterogeneity played a key role in the macroscale plastic deformation, which was attributed to the intrinsic structural heterogeneities. These findings have implications for the development of BMGCs with excellent tensile properties. [ABSTRACT FROM AUTHOR]

• Apparent liquid-liquid transition (LLT) of several Zr-Cu-Ni-Al melts have been discovered at about 300 K above the liquidus temperature. • Two different glasses are obtained by regulating LLT in these alloys, manifesting that LLT comes from the competition between two types of atomic clusters. • LLT reconstructs the atomic structure at short-range order which was seldom verified in previous work. Up to now, the research of liquid-liquid transition (LLT) has significantly improved the understanding of its liquid structure and evolution, which is crucial to addressing the longstanding problem with glass formation. However, it remains unclear how LLT affects the vitrification and structures of glasses, due to the challenge in experimentally exploring LLT in high-temperature melt well above the liquidus temperature. In the present study, an experiment is conducted to observe LLT in three Zr-Cu-Ni-Al melts at around 1450 K from both dynamic and thermodynamic perspectives. It is discovered that superheated fragility is closely associated with glass-forming ability. By controlling the melt temperature, two types of metallic glasses are obtained, showing difference in crystallization behaviors, which is attributed to the competition between crystal-like clusters and icosahedral-like clusters. Prior to the LLT, the formation of crystal-like clusters is dominant. Afterwards, the LLT promoted formation of icosahedral-like clusters becomes dominant. Due to the inherited signatures in glass, LLT is manifested by the changes in both medium-range order structure and short-range order structure. This study further reveals the pattern of microstructural evolution accompanied by LLT in high-temperature multi-component melts, which is conducive to the control on structure and properties of glasses from liquids. [ABSTRACT FROM AUTHOR]

Pre-straining was carried out on a CuZrAl bulk metallic glass (BMG), in order to understand the physical correlation between its structural heterogeneity and nano-mechanical performance. As the pre-strain increases, the studied glass remains its amorphous structure whereas the degree of local order firstly decreases and then increases, yielding a minimum value at 10 % pre-strain, and the Helmholtz activation energy (Δ F *), shear transformation zone (STZ) volume, number of atoms in the STZ (N), and the nanohardness value exhibits a similar trend. The variation in the structure and thus mechanical performance induced by pre-straining has been interpreted from the viewpoint of free volume concept. The results obtained here can be beneficial for tailoring the structure and the corresponding mechanical properties of BMGs. [Display omitted] • The physical correlation between the structure heterogeneity and nano-mechanical performance of a CuZrAl metallic glass is established. • The CuZrAl metallic glass with a pre-strain of 10 % exhibits the smallest local order degree, Helmholtz activation energy, shear transformation zone (STZ) volume, number of atoms in the STZ, and the nanohardness. • The variation in the structure and thus mechanical performance caused by pre-straining has been explained from the viewpoint of free volume concept. [ABSTRACT FROM AUTHOR]

A bulk metallic glass (BMG), Zr 46 (Cu 4.5/5.5 Ag 1/5.5 ) 46 Al 8 (ZrCuAlAg), has been prepared and systematically evaluated in terms of microstructure, corrosion resistance, wear resistance, cytotoxicity, and in vivo implantation, aiming at exploring its use as a novel biomedical material. For comparison, the above-mentioned tests were also performed on Zr 51.9 Cu 23.3 Ni 10.5 Al 14.3 , Zr 51 Ti 5 Ni 10 Cu 25 Al 9 , and Ti 40 Zr 25 Ni 12 Cu 3 Be 20 BMGs, pure Ti and Ti–6Al–4V alloys. ZrCuAlAg BMG exhibits better corrosion resistance in both NaCl and Hank's solutions than other materials. The cell culture tests indicate that the BMGs exhibit a cytotoxicity of Grades 0–1, identical with pure Ti and Ti–6Al–4V alloys. Cell morphological analysis shows that the cells were flattened and well spread out on the surfaces of the BMGs, demonstrating their good cell compatibility. Animal tests proved that the ZrCuAlAg BMG implant performed as well as Ti–6Al–4V, without any obvious inflammation reaction at the implantation sites. The excellent biocompatibility of ZrCuAlAg BMG can be attributed to its amorphous structure-related high corrosion resistance as well as its unique composition, i.e. free of toxic Ni and Be, and containing biocompatible Ag element. It suggests that the Ag-bearing ZrCuAlAg BMG with excellent biocompatibility is promising for biomedical applications. [ABSTRACT FROM AUTHOR]

Here, the effect of ion irradiation on the structure and mechanical properties of a Ti-based metallic glass has been studied. The samples maintains amorphous nature after ion irradiation. The irradiated glass exhibits higher hardness and Young’s modulus, and higher indent load at first pop-in event, which can be interpreted from the perspective of atomic-scale structural evolution. The results obtained here indicate that ion irradiation can be considered as a powerful method to finely tune the microstructure and properties of metallic glasses. [ABSTRACT FROM AUTHOR]

Annealing treatment below the glass transition temperature of Zr 55 Cu 30 Al 10 Ni 5 bulk metallic glass (BMG) specimens are investigated. Every 10 K temperature interval isothermal limited annealing treatment time will be selected to draw up time–temperature–transformation ( T – T – T ) curve. The apparent activation energy of crystallization is about 325 ± 7 kJ/mol, higher than the values of supercooled liquid region conditions. Surface hardness of the samples before and after the limited annealing treatment are tested by nanoindentation, where the spherical-like crystallization morphology indicate the higher standard deviation of surface hardness of the BMG after the limited annealing treatment. The crystallization kinetics of the Avrami exponent is 4 in accordance with spherical-like crystallization morphology. A short review on mathematical setting of the problem could distinctly give the differences of the different crystallization behaviors at different temperature regions. Avrami exponent is from 4 to 3, explaining the crystallization morphology is from spherical-like to dendritic, could be ascribed to the concepts of symmetry breaking. [ABSTRACT FROM AUTHOR]

Herein, we report high magnetocaloric performance of melt-extracted metallic glass Gd 60 Al 20 Co 20 microwires, which exhibit a large and reversible magnetocaloric effect (MCE). The isothermal magnetic entropy change (−Δ S m ) reaches as high as 10.1 J kg −1 K −1 and the refrigerant capacity (RC) has a large value of 681 J kg −1 for a field change of 5 T. The as-obtained Gd-based metallic glass microwires hold a great promise for multifunctional applications in MCE-based refrigeration of liquid nitrogen temperature range. [ABSTRACT FROM AUTHOR]

Bulk metallic glass (BMG), Zr 46 Cu 37.6 Ag 8.4 Al 8 (ZrCuAlAg), has been systematically evaluated in terms of microstructure, compressive properties, and wear resistance, aimed at exploring its use as a novel biomedical material. For comparison, the above-mentioned tests were also performed on Zr 51.9 Cu 23.3 Ni 10.5 Al 14.3 , Zr 51 Ti 5 Ni 10 Cu 25 Al 9 , and Ti 40 Zr 25 Ni 12 Cu 3 Be 20 BMGs, pure Ti and Ti–6Al–4V alloy. ZrCuAlAg BMG exhibits higher strength, higher hardness, and better wear resistance than other materials. All the results imply that the Ag-bearing ZrCuAlAg BMG with excellent mechanocompatibility will open up a new path for biomedical applications. [ABSTRACT FROM AUTHOR]

Highlights: [•] The effect of structural relaxation on the nano-mechanical behaviors of BMGs is studied. [•] The indent load at first pop-in event, the hardness and Young’s modulus are enhanced after annealing. [•] The differences in nanomechanical properties can be attributed to their different atomic structure. [Copyright &y& Elsevier]

Highlights: [•] High-quality Gd55Al25Co20 metallic glass magnetocalorific fibers were melt-extracted. [•] They show superior MCE performance versus its counterpart in BMGs. [•] They have tensile strength of 1189MPa and high security threshold of 796MPa. [•] The excellent performances result from size effect and amorphous structure. [Copyright &y& Elsevier]

Highlights: [•] The small BMG has larger free volume concentration due to faster cooling rate. [•] The wear performance changes dramatically with decreasing the sample size. [•] The variation in the wear performance is interpreted based on free volume theory. [Copyright &y& Elsevier]

Abstract: In the paper, the deformation of Ti40Zr25Ni3Cu12Be20 bulk metallic glass plate subjected to shear punching has been studied. The fractured surface of the punch-out disks consists of three characteristic zones, namely the deformation band, the fractured zone, and the burr. Vein-like patterns, river-like patterns, and the coexistence of river-like patterns plus radiating cores are found on the fractured surface as the ratio of the punch-head/die clearance to the plate thickness, i.e., the relative clearance, increases because of the changes of the stress states during shear punching. Moreover, with the increase of the relative clearance, more plastic deformation occurs, causing the increase in the height percentages of both deformation band and burr. [Copyright &y& Elsevier]

Abstract: The effect of cooling rate on the mechanical behaviors of a Ti-based bulk metallic glass has been studied using nanoindentation technique. It is found that the hardness increases, while the plastic deformation capacity gradually decreases from the edge to the center of the sample. The variation of the structural uniformity within the as-cast glassy sample may account for the cooling rate dependence of mechanical performance. [Copyright &y& Elsevier]

Abstract: It has been found that the hardness measured from different metallic glassy samples using the Oliver and Pharr scheme [Oliver WC, Pharr GM. An improved technique for determining hardness and elastic modulus using load and displacement sensing indentation experiments. J Mater Res 1992;7:1564–83] shows an apparent indentation size effect (ISE), i.e., the hardness decreases as indentation depth increases. A similar ISE of the pile-up ratio has also been found. A ribbon glassy sample fabricated at a larger cooling rate shows larger pile-up and lower hardness value than a bulk glassy sample under the same conditions. The ISE of hardness can be effectively eliminated by taking into account the different pile-up ratios at different indentation depths. [Copyright &y& Elsevier]

Abstract: The phase evolution in the transition region of a bulk Zr56.6Cu17.3Ni12.5Al9.6Ti4 amorphous alloy wedge-ingot upon annealing has been studied. The result shows that the primary crystallized metastable phase and the amorphous matrix were found to crystallize into different products. Concerning the solidification process, it is deduced that the understanding of the competitive relationships among the intermetallic phases and the amorphous phase can be described by the phase analyses of solidification, rather than the widespread investigations of the crystallization by annealing. [Copyright &y& Elsevier]

Abstract: The mechanical properties of Ti-based metallic glasses prepared with different cooling rates have been carried out using nanoindentation at different loading rates. The effect of applied loading rate and sample size on the deformation was studied. It is found that lower loading rate promotes serrations or pop-in events. The gradual disappearance of pop-in events observed on load–displacement (P–h) curves represents a transition from discrete shear band activity at low loading rates to the simultaneous operation of multiple shear bands at higher loading rates. The pop-in size was observed to be load or contact depth dependent. An obvious creep displacement, sensitive to loading rates, was observed during the holding period at the maximum load. The cooling rate employed in sample preparation significantly influences the nano-mechanical properties of the metallic glasses, in that the ribbon sample exhibits lower hardness, incipient plasticity at lower applied load and greater pile-up height than bulk samples. [Copyright &y& Elsevier]

Abstract: X-ray diffraction (XRD), high-resolution transmission electron microscopy (HRTEM), and differential scanning calorimetry (DSC) were performed to investigate the critical cooling rate and thermal stability of Ti40Zr25Ni3Cu12Be20 metallic glass. The critical cooling rate for glass formation of the studied metallic glass is determined to be as low as 3.2K/s, revealing a high glass-forming ability. The activation energies of the alloy are strongly dependent on the cooling rate during rapid solidification. Compared with the ribbon sample, the bulk sample that experiences slower cooling rate during solidification contains a greater degree of medium range orders (MRO), which favors nucleation, therefore leading to its smaller activation energies. [Copyright &y& Elsevier]

Abstract: New bulk metallic glasses are produced by substituting a few atomic percentages of iron with yttrium in the Fe45−x Cr16Mo16C18B5Y x (x =0, 1, 2, 3) alloy systems. The study shows that the optimum yttrium content in the alloy for the best glass-forming ability is 2at.%, and with this composition fully amorphous as-cast samples with a size of 6mm in diameter can be produced by the copper mold casting. The mechanism for the effect of yttrium addition on the glass-forming ability of the Fe45−x Cr16Mo16C18B5Y x (x =0, 1, 2, 3) alloys is discussed according to the effect of yttrium content in the alloy on the characteristic temperature values as measured by using DTA in this study. Furthermore, the compression tests of the bulk amorphous samples of Fe43Cr16Mo16C18B5Y2 alloy show that the room temperature compressive strength of the amorphous alloy is approximately 1824MPa. [Copyright &y& Elsevier]

• The cooling induced structural evolution of CuZr-based BMGC is in-situ studied. • The hydrostatic pressure exerts a crucial role on the martensitic transformation of B2 CuZr phase. • The thermodynamics mechanism of the phase transformation of CuZr phase is clarified. [Display omitted] In - situ high-energy X-ray diffraction and molecular dynamic simulation were employed to study the structural evolution of a B2 phase reinforced CuZr-based bulk metallic glass composite in different structural states during cryogenic treatment between 300 K and 100 K. No phase transformation occurs in the as-cast sample during cryogenic treatment, while the pre-strained sample undergoes martensitic transformation and reverse martensitic transformation. The ambient temperature, uniaxial stress, and hydrostatic pressure on the B2 CuZr phase are closely related to the phase transformation behavior of the CuZr phase in the pre-strained composite sample. Molecular dynamic simulation confirms the experimental results. The findings in this work will help to clarify the mechanism of the martensitic transformation in the B2 CuZr phase, and finely tune the structure and mechanical behaviors of CuZr-based bulk metallic glass composites. [ABSTRACT FROM AUTHOR]

[Display omitted] • Nanocrystalline Fe-containing GdTbCoAl high-entropy-metallic-glass were attained. • Curie temperature is tuned by Fe-doping in a wide temperature range of 81–108 K. • Magnetic entropy change 7.6–8.9 J kg−1 K−1 for 5 T were achieved. • The dual-phase structure with T C distribution enhances the cooling efficiency. Through designing the composition and processing approach, the non-equiatomic (Gd 36 Tb 20 Co 20 Al 24) 100-x Fe x (x = 0, 1, 2 and 3 at.%) high-entropy-metallic-glass (HE-MG) alloy microwires were successfully fabricated by melt-extraction technique. The microstructure and magnetocaloric properties of the microwires were systematically investigated. The microwires possess tunable Curie temperatures, i.e. 81–108 K, above the typical rare-earth (RE) containing HE-MG reports. The high Curie temperatures are attributed to the designed composition. Magnetocaloric response peak values of Fe-containing GdTbCoAl alloy microwires range 7.6–8.9 J kg−1 K−1 (5 T), which are comparable to those of many outstanding RE-containing magnetocaloric HE-MGs. The characteristics of the melt-extraction method, combining with compositional effects, favor the formation of amorphous and nanocrystalline phases. The increase in the cooling efficiency for microwires with higher Fe content can be attributed to the broadening of the Curie temperature distribution induced by the composition difference between nanocrystalline phase and amorphous matrix. The designed composition and the melt-extraction processing approach for Fe-containing GdTbCoAl alloys can tune their Curie temperatures towards a temperature range of natural gas liquefaction and improve their magnetocaloric properties. This demonstrates that Fe-containing GdTbCoAl HE-MG composite microwires have great potential as high-performance magnetic refrigerants. [ABSTRACT FROM AUTHOR]

In this work, deformation behaviors of a CuZrAlNb bulk metallic glass composite (BMGC) with different volume fractions of the crystalline phase were characterized using in-situ tensile tests in an optical microscope. For the studied composite, it was found that the volume fraction of the crystalline phase plays a significant role in shear band types. Shear bands which are not restrained by the crystalline phase, disappeared with increasing the crystallization volume fraction. There exists a critical volume fraction (~ 29.63 %) of the crystalline phase determining deformation behaviors of the studied composite. Beyond the critical value, this composite exhibits the homogeneous plastic deformation. Otherwise, the deformation of the BMGC is affected by shear bands which are not restrained by the crystalline phase, resulting in a decrease in the plasticity of the BMGC. Besides, the crystalline phase with a large-size bears more strain than that with a small-size in BMGCs, thereby improving their mechanical properties. [ABSTRACT FROM AUTHOR]

In this study, the effect of cryogenic testing temperatures on the deformation behavior of a CuZr-based bulk metallic glass composite (BMGC) has been investigated using in situ high energy X-ray diffraction. The yield strength and work-hardenability of the studied BMGC show an increasing trend from 298 K to 153 K. A higher yield strength at a lower temperature can be attributed to the larger difference in the volume shrinkage between the crystalline phase and the amorphous matrix. The increasing martensitic transformation degree of the crystalline phase from 298 K to 153 K results in the enhanced work-hardenability. These results lead to a better understanding of the temperature dependence of phase-transformation induced plasticity in CuZr-based BMGCs. ga1 • The yield strength of the BMGC shows an increasing trend from 298 K to 153 K. • The increase of the work-hardenability is attributed to martensitic transformation. • Martensitic transformation degree is higher at a lower temperature. [ABSTRACT FROM AUTHOR]

In this work, a long-term room-temperature aging treatment of the order of years is applied to a B2 phase-reinforced CuZr-based bulk metallic glass composite (BMGC). Presumably governed by residual stress, B19' CuZr martensitic phase gradually precipitates in the crystals after such long-term aging, while structural relaxation takes place in the glassy matrix, which finally induces precipitation of Cu 10 Zr 7 nanocrystals. Tensile tests prove that these time-dependent structural changes have a measurable effect on deformation behaviors of BMGC. The findings are helpful for understanding the thermodynamic stability and the kinetics of structural evolution of metastable alloys and have useful implications for tailoring the structure and mechanical behavior of BMGCs. Image 1 • Natural aging induces structure evolution in CuZr-based bulk metallic glass composite. • Structure stabilization occurs in both the B2 CuZr phase and the amorphous phase. • Hydrostatic pressure plays a crucial role in the structural transformation of phases. [ABSTRACT FROM AUTHOR]

• B2 CuZr phase under high stress transforms to martensite as the temperature decreases. • Molecular dynamics verifies the martensitic transformation of B2 CuZr phase. • Hydrostatic pressure plays a crucial role in phase transformation of B2 CuZr phase. In this work, the cryogenic-temperature-induced structural evolution of B2 CuZr phase-reinforced Cu 48 Zr 47.2 Al 4 Nb 0.8 bulk metallic glass composite (BMGC) is in - situ studied under tensile stress. During the cooling process from 280 K down to 80 K, the B2 CuZr phase in the nearly yielding BMGC undergoes the martensitic transformation, whereas the composite sample retains its structure at lower stress. Molecular dynamics results confirm the structural changes of the B2 CuZr phase during the cooling process. The findings will be helpful for fine tailoring the structure of CuZr-based BMGCs and thus widening their applications. [ABSTRACT FROM AUTHOR]

The enhanced magnetocaloric properties are studied in melt-extracted Gd 36 Tb 20 Co 20 Al 24 metallic glass microwires. The Curie temperature is ∼91 K for these microwires which show promising applications at liquid nitrogen range. The microwires possess spin glass phase in low temperature and spin freezing temperature is 60 K. Notably, the maximum magnetic entropy change (–Δ S M max), the relative cooling power (RCP) and the refrigerant capacity (RC) reach high values of 12.36 J kg−1K−1, 948 J kg−1 and 731 J kg−1, respectively, under a field change of 5 T. The large –Δ S M max originates from the high effective magnetic moment. Meanwhile, the spin fluctuation, the exchange integral fluctuation of metallic glass and the second order paramagnetic-ferromagnetic transition enlarge the phase transition range. Image 1 • Gd 36 Tb 20 Co 20 Al 24 metallic glass microwires were prepared by melt-extracted method. • The microwires show the maximum magnetic entropy change of 12.36 J. kg−1K−1. • The microwires exhibit refrigerant capacity of 731 J. kg−1. [ABSTRACT FROM AUTHOR]

To understand the shear banding evolution and the effect of individual shear band on deformation mechanisms of bulk metallic glass composites (BMGCs), tensile tests of CuZrAlNb BMGCs have been in situ studied. It is found that the type and sequence of shear bands are independent of volume fraction of crystalline phase. All the types of shear bands can be considered as shear bands controlled by stress affected zones (SAZs) at crystal/matrix interface and those far away from SAZs. Based on the analysis of elastic energy dissipation, the shear bands far away from SAZs play a dominant role in the deformation stability. For current BMGCs, the propagation of shear bands far away from SAZs can be delayed by reducing the average elastic energy dissipation. High Young's modulus and volume fraction of crystalline phase are effective for decreasing the average elastic energy stored in shear bands. It is expected that the obtained results can offer better understanding of deformation mechanism in bulk metallic glass composites, which should be beneficial to design bulk metallic glass composites with improved mechanical performances. Image 1 • The type and sequence of shear bands are independent of crystalline phase contents. • All types of shear bands can be classified into two categories. • The plasticity is related to the average elastic energy dissipation in shear bands. • Elastic energy can be reduced by tuning Young's modulus and stress affected zones. [ABSTRACT FROM AUTHOR]

Abstract: Compressive deformation behaviors of a cast Ti40Zr25Ni3Cu12Be20 bulk metallic glass in the test temperatures ranging from 428 to 658K were examined in a broad range of strain rates from 1.3×10−4 to 3×10−2 s−1. The alloy studied exhibits an extraordinary compressive superplastic formability within the supercooled liquid region, typically evidenced by a large compressive strain up to 0.83. The superplastic flow behaviors are strongly dependent on the test temperatures and applied strain rates. At low temperatures or high strain rates, the viscosity measured is found to dramatically decrease with increasing strain rate (i.e., non-Newtonian flow) and a stress overshoot is detected in the first steps of strain. At low strain rates or high test temperatures, the studied glass exhibits a Newtonian flow behavior. The value of activation volume increases with increasing test temperatures. [ABSTRACT FROM AUTHOR]