Formation and crystallization of bulk Pd_(82)Si_(18) amorphous alloys

Bulk amorphous Pd 82 Si 18 alloy with the largest diameter of 8 mm was prepared by water quenching the molten alloy with flux medium in a quartz tube. The calculation result indicates that the bulk Pd 82 Si 18 amorphous alloys have a low critical cooling rate ( R c) of 4.589 K/s or less. The experimental results show that purifying melt may improve glass forming ability(GFA) of undercooled melt, while liquid phase separation (LPS) of undercooled melt will decrease its GFA. There are some differences in crystallization experiments between bulk metallic glass and amorphous ribbons of Pd 82 Si 18 alloys. These include the numbers of exothermic peak, glass transition temperature T g, crystallization temperature T x, region of undercooling liquid (Δ T=T x- T g) respectively. The links of cooling rates of melt and crystallization of Pd 82 Si 18 amorphous alloys are explored.

Influence of flux treatment on the glass forming ability of Pd-Si binary alloys

Pd81Si19 amorphous alloys were prepared by combination methods of melt spinning and B2O3 flux treatment. A compari- son between the ribbons prepared from the fluxed ingots and the non-fluxed ones has been carried out. The result reveals that after fluxing treatment the glass transition temperature of the as-prepared glassy ribbons is reduced while the initial crystallization tem- perature is enhanced. It results in that the supercooled liquid region (defined as the difference between the initial crystallization tem- perature and the glass transition temperature) of the glassy alloy treated with fluxing technology has been increased from 31 to 42 K. This shows that fluxing technique can enhance the glass forming ability (GFA) of the binary alloy and improve the thermal stability of supercooled liquid of the glassy alloy.

Effect of Co substitution on the glass forming ability and magnetocaloric effect of Fe88Zr8B4 amorphous alloys

As greater attention is paid to energy consumption and global warming,magnetic refrigeration(MR)technologies based on the magneto-caloric effect(MCE)have been developed.Systems based on MR are expected to be more compact。

Effect of Rare Earth and Transition Metal Elements on the Glass Forming Ability of Mechanical Alloyed Al–TM–RE Based Amorphous Alloys

The present work aims to compare the amorphous phase forming ability of ternary and quaternary Al based alloys （Al86Ni8Y6, Al86GNi6Y6Co2, Al86NigLa6 and Al86Ni8Y45La15） synthesized via mechanical alloying by varying the composition, i.e. fully or partially replacing rare earth （RE） and transition metal （TM） elements based on similar atomic radii and coordination number. X-ray diffraction and high resolution transmission electron microscopy study revealed that the amorphization process occurred through formation of various intermetallic phases and nanocrystalline FCC Al. Fully amorphous phase was obtained for the alloys not containing lanthanum, whereas the other alloys containing La showed partial amorphization with reappearance of intermetallic phases attributed to mechanical crystallization. Differential scanning calorimetry study confirmed better thermal stability with wider transformation temperature for the alloys without La.

Fragility and glass forming ability of Al-Ni-Ce alloy melts

The fragility of Al Ni Ce alloy melts with three kinds of different compositions, Al85Ni10Ce5, Al85Ni8Ce7, Al85Ni5Ce10(mole fraction, %), was studied using oscillating vessel viscometer and differential scanning calorimetry. Their fragility parameters obtained from experiments and theoretic calculation are: 238, 228 and 335 respectively. The results indicate that these three kinds of Al Ni Ce alloy melts are very fragile liquids, which kinetically show strong non Arrhenius behaviour in the Angell plot, so they have poor glass forming ability (GFA). The alloy melt Al85Ni5Ce10 has the largest fragility parameter among the three alloy melts. In the preparation of rapidly quenched amorphous ribbons, Al85Ni10Ce5 and Al85Ni8Ce7 can gain amorphous ribbons when the rotate speed of the roller reaches 800 r/min, while for Al85Ni5Ce10 it must exceed 1 000 r/min.

Effect of Ni substitution on the formability and magnetic properties of Gd50Co50 amorphous alloy

A small amount of Ni was added into the binary Gd50Co50 amorphous alloy to replace Gd in order to obtain ternary Co50Gd50-xNx(x=1,2,and 3)amorphous alloys.Compared to the binary Gd50Co50 amorphous alloy,the Co50Gd50-xNx amorphous alloys show an enhanced Curie temperature(TC)with a weakened formability.The maximum magnetic entropy change(-Δ^Smpeak)of the Co50Gd50-xNx amorphous alloys is found to decrease with the increasing TC.The adiabatic temperature rise(ΔTad)of the Co50Gd47Ni3 amorphous alloy is superior to that of the Fe-based metallic glasses at room temperature.The variation of the TC and-Δ^Smpeak of the Gd50Co50 amorphous alloy with Ni addition,and the mechanism involved,were discussed.

Effect of Pd on GFA and Thermal Stability of Zr-based Bulk Amorphous Alloy

The effect of Pd addition on the glass-forming ability and thermal stability of the Zr55Al10Cu30Ni5-xPdx (x=0, 1, 3, 5 at. pct) alloys upon copper-mold casting has been investigated. The structure, thermal stability and microstructure were studied by X-ray diffraction (XRD), differential scanning calorimetry (DSC) and transmission electron microscopy (TEM), respectively. It was identified that a new bulk amorphous alloy with the larger supercooled liquid region Tx of 100 K is obtained with substituting Ni by 1 at. pct Pd. Furthermore, the origins that thermal stability and GFA change with increasing of Pd have also beer discussed.

Influence of B,Al and Nb addition on the glass forming ability and stability of mechanically alloyed Zr-Ni amorphous alloys

We investigated the influence of minor additions of B,Al and Nb that have representative atomic sizes on the glass forming ability (GFA) and stability of Zr-Ni amorphous alloys during mechanical alloying. The results show that the minor addition of B,Al or Nb does not shorten the initial time of the full amorphization reaction or improve the glass forming ability of the Zr-Ni alloys at a low rotation speed. However,B addition can effectively improve the mechanical stability of the amorphous phase against mechanically induced crystallization. Furthermore,the amorphous phase gradually transforms into a metastable fcc-phase with increasing milling time. The addition of Al and Nb that have similar atomic sizes has a similar effect on the GFA and the mechani-cal stability of the Zr-Ni amorphous phase. Moreover,Al and Nb addition can alter the crystallization behavior and improve the thermal stability of the Zr-Ni amorphous phase.

Formation and properties of high Fe-content Fe-(B-Si)-Zr bulk amorphous alloys

The present work is devoted to the development of Fe-（B-Si）-Zr amorphous alloys with high glass-forming ability and good magnetic properties. Using the cluster-plus-glue-atom model proposed for ideal amorphous structures, [FeFe11B3Si]（Fe1-xZrx） was determined as the cluster formula of Fe-（B-Si）-Zr alloys. The glass formation and thermal stability of the serial alloys, namely, [FeFel^B3Si]（Fel_xZrx） （x = 0, 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.75, and 1.0）, were studied by the combination of copper mold casting, X-ray diffraction, and differential thermal analysis techniques. The maxima of glass-forming ability and thermal stability were found to occur at the compositions of [FeFe11B3Si] （Fe0.6Zr0.4） and [FeFe11B3Si]（Fe0.5Zr0.5）. The alloys can be cast into amorphous rods with 1.5 ram diameter, and upon reheating, the amorphous alloys exhibit a large undercooled liquid span of 37 K. The saturation magnetization of the [FeFe11B3Si]（Fe0.5Zr0.5） amorphous alloy was measured to be 1.4 T.

Design of FeSiBPCu soft magnetic alloys with good amorphous forming ability and ultra-wide crystallization window

The Fe_(81.3)Si_(4)B_(13–x)PxCu_(1.7) soft magnetic alloys with high Cu and proper P elements addition were synthesized with the aim of ensuring the amorphous forming ability(AFA)while expanding the crystallization window(CW).It is found that the atomic ratio of P/Cu of∼3 is advantageous for AFA whereas a small amount of P addition promotes the precipitation ofα-Fe grains and excessive P addition induces surface crystallization behavior of the present alloys.High Cu concentration can expand the annealing temperature(Ta)window whereas proper P addition effectively expands the annealing time(ta)window.The Fe_(81.3)Si_(4)B_(13-x)PxCu_(1.7) soft magnetic alloy was successfully synthesized with a large Ta window of up to 130°C and ta window of 90 min,which is a breakthrough for nanocrystalline alloys with high saturation magnetization.Microstructure analysis reveals that the ultra-wide CW is related to the unique nucleation mechanism,that is,theα-Fe grains are precipitated attaching to the Cu or CuP clusters and enveloping the Cu clusters,resulting in the high number density ofα-Fe nanocrystals.The ultra-wide CW promises the potential material in flexibly choosing the annealing process according to the performance.

Glass-forming ability and corrosion performance of Mn-doped Mg-Zn-Ca amorphous alloys for biomedical applications

In the present work, ribbon and 2-mm rod samples of Mg-Zn-Ca-Mn alloys were prepared by meltspinning and copper mold injection methods, respectively. Effects of Mn doping on glass-forming ability and corrosion performance in simulated body fluid of Mg65Zn30Ca5 alloy were studied through X-ray diffraction, scanning electron microscopy, differential scanning calorimeter, and electrochemical and immersion tests. Results show that with the Mn addition increasing, all the ribbon samples are completely in amorphous state. However, the microstructure of 2-mm rod samples transfers from fully amorphous for the Mn-free alloy to almost polycrystalline state with precipitated Mg, Mn, and MgZn phases. Glass-forming ability of Mg65Zn30Ca5 alloy is decreased by Mn addition. Results of electrochemical and immersion tests demon- strate that the Mn-doped samples exhibit more negative corrosion potential and larger corrosion current density, suggesting that the corrosion resistance decreases with doping amount of Mn element increasing.

A comparative study of the structure and crystallization of bulk metallic amorphous rod Pr60Ni30Al10 and melt-spun metallic amorphous ribbon Al87Ni10Pr3

Pr-based bulk metallic amorphous （BMA） rods （Pr60Ni30Al10） and Al-based amorphous ribbons （Al87Ni10Pr3） have been prepared by using copper mould casting and single roller melt-spun techniques, respectively. Thermal parameters deduced from differential scanning calorimeter （DSC） indicate that the glass-forming ability （GFA） of Pr60Ni30Al10 BMA rod is far higher than that of Al87Ni10Pr3 ribbon. A comparative study about the differences in structure between the two kinds of glass-forming alloys, superheated viscosity and crystallization are also made. Compared with the amorphous alloy Al87Ni10Pr3, the BMA alloy Pr60Ni30Al10 shows high thermal stability and large viscosity, small diffusivity at the same superheated temperatures. The results of x-Ray diffraction （XRD） and transmission electron microscope （TEM） show the pronounced difference in structure between the two amorphous alloys. Together with crystallization results, the main structure compositions of the amorphous samples are confirmed. It seems that the higher the GFA, the more topological type clusters in the Pr-Ni-Al amorphous alloys, the GFAs of the present glass-forming alloys are closely related to their structures.

Influences of preparation techniques on glass-forming ability of Fe-P-B-Si-C amorphous alloys

It has been widely accepted that the ultrafast cooling rate is required for the glass formation of amorphous alloys. Here, the larger glass-forming ability （GFA） of Fe76P5（B0.5Si0.3C0.2）19 amorphous alloy was achieved by water quenching at lower cooling rate under argon atmosphere. Cylindrical rods with diameters of 1-2 mm were prepared by water quenching without flux treatment, Cu-mold injection casting, and Cu-mold suction casting, respectively. The influences of the preparation techniques with different cooling rates on GFA, thermal property, and nucleation/growth behavior were examined. The critical diameter of the Fe76P5（B0.5Si0.3C0.2）19 amorphous alloys is 1.7 mm for water quenching while smaller than 1.0 mm for injection casting. Microstructure analysis indicates that the crystallization and solidification processes are quite different between the water-quenched and the injection-cast rods. These findings could deepen fun-damental understanding on the relationship between the cooling rate, techniques, and GFA of Fe-based amorphous alloys.

The relationship between viscosity and glass forming ability of Al-(Ni)-Yb alloy systems

The dynamic viscosity of Al-Yb and Al-Ni-Yb superheated melts was measured using a torsional oscillation viscometer. The results show that the temperature dependence of viscosity fits the Arrhenius law well and the fitting factors are calculated. The amorphous ribbons of these alloys were produced by the melt spinning technique and the thermal properties were characterized by using a differential scanning calorimetry (DSC). E (the activation energy for viscous flow), which reflects the change rate of viscosity, has a good negative relation with the GFA in both Al-Yb and Al-Ni-Yb systems. However, there is no direct relation between liquidus viscosity (ηL) and GFA. The superheated fragility M can predict GFA in Al-Yb or Al-Ni-Yb alloy system.

Glass forming ability of Zr-and Fe-based alloys at quenching from melts

The master alloy ingots (MAI) with the nominal composition Zr 52.5 Ti 5Cu 17.9 Ni 14.6 Al 10 and Fe 61 Co 7Zr 10 Mo 5W 2B 15 (at%) were prepared by arc melting in Ti gettered Ar atmosphere. The Zr based buttons of 6 mm and 9 mm in diameter were fully amorphous, but those of 13 mm in diameter experienced crystallization. The glass forming ability (GFA) of Fe based alloys was relatively lower, and the buttons obtained were fully crystallized. The microhardness of the Zr based buttons was about 500(Hv), and the Fe based rod obtained by injection technique exhibited a high Vickers hardness of 1329. In addition, an amorphous crystalline transition layers were observed in both the buttons and the rods.

Amorphous in a Zr-IQC-DQC pseudo-ternary alloy system

A pseudo-ternary alloy system was constructed by combining an icosahedralquasicrystal (IQC), a decagonal quasicrystal (DQC), and Zr into one alloy system. Differentproportions of Zr were added to pseudo-binary alloy IQC_(80)DQC_(20) (mass fraction in %);Structural evolution in these alloys was discussed. An amorphous alloy composition was found in thissystem and a melt-spinning amorphous alloy was produced in this composition. Through DSC analysis,the amorphous alloy exhibits high glass forming ability comparable to that of the InoueZr_(65)Al_(7.5)Cu_(17.5)Ni_(10) amorphous alloy.

Formation of new Zr-Ti-Cu-Ni-Be-C bulk amorphous alloy

The formation of the new bulk amorphous Zr Ti Cu Ni Be C alloy with high strength is reported. The effects of the small size atoms on the glass forming ability, strength and thermal stability of the amorphous alloy are investigated. The formation mechanism of the bulk amorphous alloy is discussed.

Formation and performance of new Zr-Ti-Cu-Ni-Be-Fe bulk amorphous alloy

The formation of the new Zr-Ti-Cu-Ni-Be-Fe bulk amorphous alloy with high strength is reported. The effects of the iron atom on the glass forming ability, hardness, susceptibility and thermal stability of the amorphous alloy are investigated. The role of the iron in the formation of the bulk amorphous alloy is discussed.

Crystallization Behaviour and Mechanical Properties of Zr65Cu18Ni9A18 Bulk Metallic Glass

Designing and synthesis of cost effective bulk metallic glasses （BMGs） has been of considerable interest during the last decade so that they can be made commercially viable. Among these, Zr-based BMGs have been reported extensively due to their attractive properties, An alloy having composition Zr65Cu18Ni9A18 was designed and synthesized using 2-3 N pure materials by Cu mould casting. The alloy was characterized by X- ray diffraction （XRD）, scanning electron microscopy （SEM）, energy dispersive X-ray spectroscopy （EDS） and high temperature differential scanning calorimetry （DSC）. Thermal parameters like supercooled liquid region △Tx, reduced glass transition temperature Trg, γ and δ parameters were evaluated. Mechanical properties like microhardness, nanohardness, elastic modulus and fracture strength were measured. The alloy showed wide supercooled liquid region of 129＋1 K with improved thermal stability. The alloy has considerable fracture strength along with fair amount of ductility.