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In this work, a rapid and controllable ultrasonic vibration method for forming Al-based metallic glass at room temperature is proposed. This method can dramatically improve the forming ability of Al-based metallic glasses, which are virtually brittle at room temperature and have almost no supercooled liquid region at high temperatures. Under ultrasonic vibration, Al-based metallic glasses exhibited obvious plastic flow, with a maximum deformation degree up to 58% and an average deformation degree up to 43%. It is worth mentioning that no crystalline peaks were found on the X-ray diffraction patterns after deformation under ultrasonic vibration, and the mechanical properties remained the same as the primary sample. The present results provide a new approach for the deformation and forming of Al-based metallic glasses, which can significantly broaden their applications.

In this work, magnetocaloric and magnetoresistance properties of Fe-based (Fe 0.402 Co 0.201 Ni 0.067 B 0.227 Si 0.053 Nb 0.05 ) 100 - x Cu x (x = 0, 0.5, 0.75, 1) amorphous ribbons formed by melt-spinning method and the effect of Cu on these properties were investigated. Curie temperature ( T C ) was not changed with the addition of Cu up to 0.5% to the composition. On the other hand, for Fe-based (Fe 0.402 Co 0.201 Ni 0.067 B 0.227 Si 0.053 Nb 0.05 ) 100−x Cu x (x = 0.75 and 1), T C increased from 505 K (for x = 0.5) to 526 K (for x = 0.75) and almost remain constant for x = 1. Maximum magnetic entropy change (−Δ S M ) max and refrigeration capacity (RC) values were found to be in the range of 0.62–1.25 Jkg − 1 K − 1 and 62–158.75 Jkg − 1 respectively for (Fe 0.402 Co 0.201 Ni 0.067 B 0.227 Si 0.053 Nb 0.05 ) 100 − x Cu x (x = 0, 0.5, 0.75, 1) amorphous ribbons under a maximum field of 2 T. These values are comparable with those of previously studied Fe-based metallic glasses. In addition, the maximum temperature dependent magnetoresistance (MR (%)) values for (Fe 0.402 Co 0.201 Ni 0.067 B 0.227 Si 0.053 Nb 0.05 ) 100 − x Cu x (x = 0, 0.5, 0.75, 1) were found to be 125, 17, 7, and 1% around the Curie temperatures under an applied field of 1 T, respectively. The magnetoresistance values of Cu-free Fe-based glassy alloy are higher than those of Cu-doped alloys. The results show that appropriate amount of Cu substitution (x = 0.75, 1) can enhance the RC and (−Δ S M ) max . The suitable RC, large magnetoresistance, good thermal stability, and negligible hysteresis offer that these Fe-based glassy alloys exhibit promising applications as high-temperature magnetic refrigerants and multi-functional materials working in the temperature range of 400–600 K.

WOS:000393819100002 In this work, Co-based (Co0.402Fe0.201Ni0.067B0.227Si0.053Nb0.05)(100-x) Cu-x bulk glassy alloys (BMG) with 2 mm diameters were formed by suctioncasting method and effect of Cu in this system's thermal stability, glass forming ability and magnetic properties were also investigated. The curves of thermal analysis, obtained using differential scanning calorimetry, show that (Co0.402Fe0.201Ni0.067 B0.227Si0.053Nb0.05)(100-x) Cu-x (x = 0-2) has supercooled liquid region (Delta T-x) of about 45 K, and reduced glass transition temperature (T-g/T-l) lies in the range from 0.663 to 0.678. The saturation magnetisation (J(s)) and coercivity (H-c) for ascast BMG were in the range of 0.46 T-0.65 T and 13 A/m, respectively. Commission of Scientific Research Projects of Uludag UniversityUludag University [KUAP(F)-2015/50, KUAP(F)-2013/25] This work was partially supported by the Commission of Scientific Research Projects of Uludag University [Project number KUAP(F)-2015/50], [Project number KUAP(F)-2013/25].

The magnetocaloric and magnetoresistance properties of amorphous Co-based (Co0.402Fe0.201Ni0.067B0.227Si0.053Nb0.05)(100-x)Cu-x (x=0, 0.5, 0.75 and 1) ribbons were investigated. Cu additions changed the crystallisation temperature (T-x) and the Curie temperature (T-C). The saturation magnetisation (M-s) and coercivity (H-c) for alloys were in the range of 65.51-38.49 emu/g and 1.99-6.84 A/m, respectively. Under an applied magnetic field change of 2.2 T, the (-S-M)(max) for (Co0.402Fe0.201Ni0.067B0.227Si0.053Nb0.05)(100-x)Cu-x with x=0, 0.5, 0.75 and 1 are 0.77, 0.71, 0.89 and 0.67 Jkg(-1)K(-1), respectively. The values of refrigeration capacity (RC) for the as-spun glassy alloys are comparable with those of previously studied Fe-based metallic glasses such as Fe80B10Zr9Cu1, (Fe0.76B0.24)(96)Nb-4 and Fe82Ni2Zr6B10. In addition, the maximum magnetoresistance (MR) values for (Co0.402Fe0.201Ni0.067B0.227Si0.053Nb0.05)(100-x)Cu-x with x=0, 0.5, 0.75 and 1 are found to be 110, 38, 23 and 1% around the Curie temperatures under an applied magnetic field change of 1 T, respectively. With good RC, negligible hysteresis due to very low coercivity values and large magnetoresistance, these Co-based amorphous alloys can be used as the high temperature magnetic refrigerants and multifunctional applications working in the temperature range of 450-600K.

Vitrification from physical vapor deposition is known to be an efficient way for tuning the kinetic and thermodynamic stability of glasses and significantly improve their properties. There is a general consensus that preparing stable glasses requires the use of high substrate temperatures close to the glass transition one, Tg. Here, we challenge this empirical rule by showing the formation of Zr-based ultrastable metallic glasses (MGs) at room temperature, i.e., with a substrate temperature of only 0.43Tg. By carefully controlling the deposition rate, we can improve the stability of the obtained glasses to higher values. In contrast to conventional quenched glasses, the ultrastable MGs exhibit a large increase of Tg of ∼60 K, stronger resistance against crystallization, and more homogeneous structure with less order at longer distances. Our study circumvents the limitation of substrate temperature for developing ultrastable glasses, and provides deeper insight into glasses stability and their surface dynamics., Producing ultrastable metallic glasses has always been associated with substrates heated close to the glass transition temperature. Here, the authors show that reducing the deposition rate of the metallic glass on a cold substrate produces ultrastable metallic glasses with remarkably improved stability.

A new Fe-based bulk metallic glass with superior glass-forming ability (GFA), Fe46Cr15Mo14C15B6Nb4, was developed based on the Fe-Cr-Mo-C-B alloy system by minor addition of Nb. The effects of Nb addition on glass formation of the Fe-50 xCr15Mo14C15B6Nbx (x = 0, 2, 4 and 6 at.%) alloys were investigated. The optimum addition content of Nb was determined as 4 at.% by X-ray diffraction and differential scanning calorimeter analysis. A fully amorphous rod sample with 3 mm in diameter was produced by using commercial-grade raw materials and a copper mold casting technique. This alloy shows an ultimate compressive strength of 1920 MPa and Vicker's hardness 1360 H-V, which is two to three times that of conventional high strength steel and suggests a promising potential for applications combining outstanding corrosion and wear resistance properties. The crystallization kinetics studies found that the activation energies for glass transition, onset of crystallization and crystallization peak were higher than those of other reported Fe-based bulk metallic glasses. The value of the fragility parameter m for the Fe46Cr15Mo14C15B6Nb4 alloy was calculated to be 34, indicating that the Fe-Cr-Mo-C-B-Nb alloy system is a strong glass former according to the Angell's classification scheme. It is inferred that the more sequential change in the atomic size, the generation of new atomic pairs with large negative heats of mixing and the amount of oxygen in the molten liquid neutralized into Nb oxides provide a synergetic effect for the remarkably improved GFA and thermal stability. (C) 2014 Elsevier B.V. All rights reserved.

Apatite formation in the living body is an essential requirement for artificial materials to exhibit bone-bonding bioactivity. It has been recently revealed that sulfonic groups trigger apatite nucleation in a body environment. Organic-inorganic hybrids consisting of organic polymers and the sulfonic groups are therefore expected to be useful for preparation of novel bone-repairing materials exhibiting flexibility as well as bioactivity. In the present study, organic-inorganic hybrids were prepared from hydroxyethylmethacrylate (HEMA) in the presence of vinylsulfonic acid sodium salt (VSAS) and calcium chloride (CaCl(2)). The bioactivities of the hybrids were assessed in vitro by examining the apatite formation in simulated body fluid (SBF, Kokubo solution). The hybrids deposited on the apatite after soaking in SBF within 7 days. Tensile strength measurements showed a tendency to increase with increases in VSAS and CaCl(2) content. It was assumed that this phenomenon was attributed to the formation of cross-linking in the hybrids.

Three glass-forming alloy compositions were chosen for ribbon production and subsequent electron microscopy studies. In situ tensile testing with transmission electron microscopy (TEM), followed by ex situ TEM and ex situ scanning electron microscopy (SEM), allowed the deformation processes in tensile fracture of metallic glasses to be analysed. In situ shear band propagation was found to be jump-like, with the jump sites correlating with the formation of secondary shear bands. The effect of structural relaxation by in situ heating is also discussed. Nanocrystallization near the fracture surface was observed; however, no crystallization was also reported in the same sample and the reasons for this are discussed. Both the TEM and the SEM observations confirmed the presence of a liquid-like layer on or near the fracture surface of the ribbons. The formation of a liquid-like layer was characterized by the vein geometries and vein densities on the fracture surfaces and its dependence on shear displacement, 6, is discussed. A simple model is adapted to relate the temperature rise during shear banding to the glass transition and melting temperatures and this is used to explain the variety of fracture surfaces which are developed for macroscopically identical tensile testing of metallic glasses together with features which exhibit local melting. (c) 2007 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

The role of each oxide component on the structure of molten glass and on their densification and crystallization behaviours is expected to be more easily assessed for compositions comprising a small number of components. In the present work, binary (Li2O-SiO2), ternary (Li2O-Al2O3-SiO2), and quaternary (Li2O-K2O-Al2O3-SiO2) glass compositions were selected. The aim was to investigate the relationships between the compositions and structure of the glasses, namely, the effects of each component on the extent of liquid-in-liquid phase separation, their thermal behaviour and the phase assemblage in the disilicate glass-ceramics. The distribution of structural units in the experimental glasses was assessed using Si-29 MAS-NMR spectroscopy. Adding Al2O3 played a dual role as network former and modifier when added to the binary system by enhancing Q(2) and diminishing Q(3) structural units. The processing window for sintering, the difference between the onset of crystallisation and glass-transition temperature (T-c-T-g), was too narrow for the less polymerised network structures (binary and ternary systems), hindering the densification of the corresponding glass powder compacts. Oppositly, compositions in the quaternary system featured excellent densification behaviour coupled with high mechanical strength. These features derive from a more rigid glass network comprising four coordinated (AlO4/2)(-) units and K+ cations in its vicinity. (C) 2013 Elsevier Ltd and Techna Group S.r.l. All rights reserved.

A stainless steel powder of a mixed amorphous and crystalline structure was HVOF sprayed in an effort to produce coatings with a large glass fraction. In the first part of this work, the microstructure and annealing behavior of powder and coatings are studied. The coatings consisted of a glassy part and a martensitic part, the latter with boride, borosilicide and boro-carbide dispersions. The annealing behavior of powder and coatings is characterized by glass crystallization and martensite tempering. Annealing of the powder leads to complete microcrystallization of the glassy part, whereas annealing of the coatings eventually leads to nanocrystallization of the residual glass phase. In the second part, the effects of selected spraying parameters (oxygen-to-fuel ratio, powder feed rate, spraying distance and spraying stages) on characteristic coating properties are investigated by means of the Taguchi analysis. The oxygen-to-fuel ratio mostly affected the coating hardness and porosity. The powder feed rate had a significant effect on all the coating properties but mostly on the deposition rate and crack extension force. Spraying in stages significantly increased the deposition rate, whereas it promoted coating amorphicity. A spraying experiment under the optimum conditions determined by the Taguchi analysis, showed a good fit between the predicted and the attained property values. (C) 2011 Elsevier B.V. All rights reserved. Surface & Coatings Technology

International audience; Using real space pair distribution functions derived from high precision x-ray diffraction data, the local atomic structure of Zr-Ni and Zr-Ni-Al metallic glasses was investigated. Unlike Zr-Cu metallic glasses, the structure of Zr-Ni metallic glasses cannot be approached with an ideal solution model, due to strong attractive interactions between Zr- and Ni atoms, which promote chemical short range order. Addition of Al can be beneficial for the glass forming ability of Zr-Ni metallic glasses. The atomic size of Al, being intermediate to those of Zr- and Ni and the strongly attractive interactions between Zr-Al and Zr-Ni atoms can lead to highly negative volumes of mixing Delta V/(mix), and to denser atomic structures, reduced atomic mobility in the liquid and easier suppression of crystallization in the undercooled liquid state

In the field of transmission electron microscopy (TEM), fundamental and practical reasons still remain that hamper a straightforward correlation between microscopic structural information and deformation mechanisms in materials. In this article, it is argued that one should focus in particular on in situ rather than on postmortem observations of the microstructure. This viewpoint has been exemplified with in situ straining and in situ compression studies on metallic glasses. In situ TEM straining of amorphous metals permits an evaluation of the thickness of the liquid-like layer (LLL) formed because of heat evolution after shear band development. The experimental evaluation confirms that the thickness of a LLL present at the last moment of fracture substantially exceeds the generally accepted thickness of a shear band. In situ TEM and in situ SEM compression experiments on metallic glass pillars lead to the conclusion that smaller sized pillars deform more homogeneously than larger sized pillars. Microsc. Res. Tech. 72:250-260, 2009. (C) 2009 Wiley-Liss. Inc.

International audience; The phase components and microstructure of as-cast Ti41.5Cu37.5Ni7.5Zr2.5Sn5Hf5Si1 glass forming alloy was investigated by differential scanning calorimetry (DSC), scanning electron microscopy and in-situ neutron diffraction studies. For diameters above 3 mm the samples present small crystals identified as the Ti5Sn3Cu and cubic Ti(CuNi) phases. Crystallization studies in the DSC furnace and in-situ neutron diffraction reveal that the cubic titanium phase is TiNi(Cu) with the Pm-3m space group and not the beta-Ti phase. The evolution of phases above T, show that the TiNi phase is metastable and decomposes at Tx=727 K to form the gamma-TiCu phase. The Ti5Sn3Cu phase does not evolve in this temperature range. At room temperature by compression measurements, the alloy with 2 mm diameter shows a high failure limit of 2120 MPa with 2,1% of plasticity.

The effect of low amounts of Cr on glass forming ability and corrosion behavior of Fe(65-x)CrxMo14C15B6 (x = 0, 2, 4, 6, 8,10 at.%) ribbons have been studied. It was found that the reduced glass transition temperature (T-rg) do not change significantly with Cr content. The glass forming ability (GFA) of this system is evaluated by the gamma(m), delta and omega parameters and the alloys containing 4 and 6 at.% were found to be the best glass formers in this system. The temperature interval of the supercooled liquid region (Delta T-x) changed with Cr and was enlarged from 35 K at x = 0 to 50 K at x = 4. Corrosion rates measured by immersion tests in H2SO4 decreased with an increase of chromium content in the alloys. The electrochemical measurements indicate that the alloys containing more than 4 at.% of Cr are spontaneously passivated with low current densities in 0.1 N H2SO4 whereas the alloys with Cr content

Bulk Metallic Glasses (BMG) are metallic alloys that have the ability to solidify in an amorphous state. BMGs show enhanced properties, for instance, high hardness, strength, and excellent corrosion and wear resistance. BMGs produced by conventional methods are limited in size due to the high cooling rates required to avoid crystallization and the associated detrimental mechanical properties. Additive manufacturing (AM) techniques are a potential solution to this problem as the interaction between the heat source, e.g., laser, and the feedstock, e.g., powder, is short and confined to a small volume. However, producing amorphous parts with AM techniques with mechanical properties comparable to as-cast samples remains a challenge for most BMGs, and a complete understanding of the crystallization mechanisms is missing. This review paper tries to cover recent progress in this field and develop a thorough understanding of the correlation between different aspects of the topic. The following subjects are addressed: (i) AM techniques used for the fabrication of BMGs, (ii) particular BMGs used in AM, (iii) specific challenges in AM of BMGs such as the control of defects and crystallization, (iv) process optimization of mechanical properties, and (v) future trends.