Zr-based Glassy Alloys Research Articles

Plastic Zr-Al-Ni-Cu-Ag bulk glassy alloys containing quasicrystalline or β-Zr plus ω-Zr phases

Zr70–76Al7–7.5Ni13–15Cu2Ag2–5 glassy alloys were prepared by melt-spinning with Zr contents up to 76 at.%, greatly exceeding the highest Zr content of 70 at.% previously reported for Zr-based glassy alloys exhibiting a calorimetric glass transition. The 70–72Zr and 74Zr alloys were also cast as bulk rods up to 1.5 mm in diameter with glass and [glass + β-Zr + ω-Zr] phases, respectively, by ejection copper-mold casting. The crystallization temperature and Vickers hardness Hv for the glassy ribbons decrease with increasing Zr content from 70 to 76 at.%. The glassy rods show high yield strength (σy) of 1225–1346 MPa, high fracture strength (σf) of 1497–1499 MPa, and large compressive plastic strain (εp) of 9.7–3.2% for the 70–72Zr alloys. Similarly, the 74Zr rod with [glass + β-Zr + ω-Zr] phases shows σy of 1325 MPa, σf of 1472 MPa, εp of 2.4%. The 76Zr thick ribbon with [glass + β-Zr + ω-Zr] phases shows, in tension, high σy of 890 MPa, σf of 988 MPa, and plastic elongation of 0.3%. The Zr-rich glassy ribbons crystallize, showing three exothermic peaks upon heating. The first-stage peak is due to the precipitation of icosahedral quasicrystal (IQ) for the 70–72Zr ribbons, and β-Zr + ω-Zr for the 74–76Zr ribbons. These annealing-induced mixed-phase ribbons with Zr content above 72 at.% exhibit good bending plasticity, even though their HV is about 41% higher than for the as-spun glassy ribbons. Similarly, the 70Zr bulk rod, with [glass + IQ] phases obtained by annealing, shows a distinct increase in σy and σf to 1485 and 1575 MPa, respectively, as well as εp of 0.6%. Thus, the plastic Zr-rich bulk rods with glass, [glass + IQ], and [glass + β-Zr + ω-Zr] phase mixtures are encouraging for the future development of a new type of high-strength structural material.

Formation of a Ni- and Be-free Zr-based glassy alloy in centimeter scale

A Ni- and Be- free Zr-Al-Cu-Y glassy alloy in centimeter scale has been developed and understood via clusters in this letter. Glass-formers in Zr-Al-Cu system was understood and constructed by Zr-Al and Zr-Cu clusters proportionately. Clusters Cu-Cu7Zr5 and Al-Al2Zr8, which conform to the topological packing compact criterion, were chosen and used. The ratio between clusters is determined by electrons per atom ratio. Alloy with highest GFA located at Zr48.65Cu43.24Al8.11 which could be regarded as 0.5Al-Al2Zr8 + Cu-Cu7Zr5. Its critical diameter is 6 mm, superior than Zr50Cu40Al10 of which critical diameter is about 3 mm at the same laboratory environment. Furthermore, 2 at.% Y alloying greatly enhances GFA leading to centimeter scale. Its reason was also discussed from the aspect of clusters. The results in this letter might provide a way of designing good glass-formers, understanding microalloying and expand the application range of amorphous alloys.

Formation, structure and properties of pseudo-high entropy clustered bulk metallic glasses

The formation, structure and properties of clustered glassy alloys were reviewed in correlation with pseudo-high entropy (PHE) type alloy components on the basis of our recent data. The features of the PHE bulk metallic glasses (BMGs) in Fe- and Zr-based alloy systems were also presented in comparison with high entropy glassy and crystalline alloys. The selection of PHE alloy compositions enables the formation of a clustered glassy phase in the wide temperature range below the onset temperature of the second exotherm peak. The presence of the glassy phase without appreciable precipitates even after the completion of the first exotherm peak has not been reported so far in spite of a large number of crystallization data on amorphous and glassy alloys. The precipitates at the temperatures just below the second exotherm peak for PHE Fe- and Zr-based glassy alloys are big cubic χ-FeCoNiCrMo(B) with a lattice parameter of about 0.90 nm and Zr2M (M = Al,Fe,Co,Ni,Ag) with a lattice parameter of about 1.2 nm, respectively. The precipitation of these metastable phases with large unit volumes needs long-range atomic rearrangements, but the atomic diffusivity in the PHE glassy alloys is very low, resulting in the formation of the clustered glassy phase. The clustered glassy alloys exhibit high strength and unprecedented plasticity for PHE Zr–Nb–Al–Ni–Cu BMGs, very high coercive force for Nd-Fe-Al BMGs, good soft magnetic properties in conjunction with better plasticity for PHE Fe–B–Si–P–Cu BMG and high thermal resistance to crystallization for PHE Zr–Al–Ni–Cu–Ag BMGs, and hence are expected to become important as a new type of engineering glassy material.

Enhanced room-temperature plasticity in a Zr-based glassy alloy by micro-arc oxidation treatment

In this work, an enhanced room-temperature plasticity was achieved in a Zr62.8Cu15Co9.2Ti6Al7 glassy alloy through the application of micro-arc oxidation (MAO) treatment. After treated for 15 and 30 min, the glassy alloy specimen exhibited an enhanced plastic strain of 5.5% and 7.9%, respectively. Both the introduction of nucleation sites for shear band at the coating/substrate interface owing to stress concentration and the physical constraint effect for the propagating shear bands from the in-situ formed coating are responsible for the enhanced plasticity. This finding may open a new avenue for developing ductile metallic glasses from a surface modification aspect.

Factors Influencing Oxidation Behavior of Metallic Glasses

The extent of oxidation and mechanism involving glassy and nanocrystalline phases are found to be different than that in case of normal crystalline metals and alloys. A short review on oxidation behavior of metallic glass and nanocrystalline alloys is presented in the light of work by the present authors and other researchers. The main factors, which are important in controlling the oxidation of metallic glass, are: (i) structure of glass and its devitrified states, (ii) composition of the alloy, and (iii) structure of the oxide layer. Hence, these factors are discussed with the help of isothermal and non-isothermal oxidation both in air and in the presence of oxygen of a number of Zr-based glassy alloys. The oxidation resistance of the glassy alloys decreases in the following order: microcrystalline alloy > fully nanocrystalline alloy > partially nanocrystalline alloy > relaxed amorphous alloy > quenched amorphous Zr-based alloy.

Microstructure, mechanical properties, and crystallization behavior of Zr-based bulk metallic glasses prepared under a low vacuum

The present work is devoted to an investigation of the microstructure, deformation behavior and kinetics of crystallization of Zr-based glassy alloys produced in a low vacuum environment. The data obtained indicate that small additions of rare earth (RE) metals, such as Dy, Gd, Er, to a Zr62.5Cu22.5Fe5Al10 alloy are likely to suppress heterogeneous nucleation of impurities, and thus, increase the glass forming ability (GFA), which allows obtaining glassy ingots up to 5 mm diameter even under a low vacuum. The structure of the alloys consisted of a glassy matrix and a small fraction of RE oxides. The large difference between the enthalpies of the oxide formation of copper and RE elements is responsible for the reduction of copper concentration in the regions near the oxides. According to the kinetics parameters of crystallization, the highest thermal stability observed in a Gd-bearing alloy corresponds to its good GFA. The maximum compression strength was achieved in the alloy containing 0.5 at.% of Dy. At the same time, the optimal combination of strength and plasticity, with the fracture strength of 1890 MPa and the plastic deformation of 3.3%, was observed in the alloy containing 1 at.% of Gd. A finite element modeling (FEM) analysis showed that equiaxed oxide particles can prevent propagation of a single shear band and promote generation of multiple shear bands.

Microstructural development at weld interface between Zr-based glassy alloy and stainless steel by resistance microwelding

Zr-based bulk metallic glasses are expected to be welded to conventional structural alloys. Dissimilar welding of metallic glasses to stainless steel was carried out by resistance microwelding. The metallurgical analysis of the weld interface revealed the welding mechanism. A thin reaction layer was formed between the two liquid materials. The melting of stainless steel should be limited to obtain sound joints.

Investigation of viscosity and crystallization in supercooled-liquid region of Zr-based glassy alloys

Using viscosity measurement method and in-situ heating synchrotron radiation, the viscosity of the (Zr0.55Al0.1Ni0.05Cu0.3)100−xYx (x=0, 0.5, 1, 2) bulk metallic glasses (BMGs) in their supercooled liquid regions (SLRs) and the in-situ heating nucleation were investigated, respectively. In the SLR, the (Zr0.55Al0.1Ni0.05Cu0.3)99Y1 metallic glass which shows distinct plastic strain in compression exhibits higher viscosity than the other three BMGs, however their Poisson's ratios are almost the same. The synchrotron diffraction results show that crystallization happened in the SLR of the (Zr0.55Al0.1Ni0.05Cu0.3)99Y1 glassy alloy, which could be the reason for the higher viscosity and larger plastic strain in compression compared to the other three alloys. The fracture surfaces of the glassy alloys were observed and analyzed.

Study on continuous casting of bulk metallic glass

Continuous casting method for massive production of steel, aluminum, copper or other crystalline alloy ingot is a very important industrial technology for its low energy consumption and high productivity. In this study, a new continuous casting method was developed for the massive production of bulk metallic glass ingot with centimeter-scale diameter without length limitation. An intermittent withdrawal procedure was practiced for continuous casting of bulk glassy alloy. The new developed continuous casting method can provide a cooling speed as high as that provided by the stationary mold casting method. A Zr-based glassy alloy rod with a diameter of about 10 mm and length of tens of centimeters was prepared by the continuous casting method for the first time.

Tensile deformation behaviour of Zr-based glassy alloys

This paper presents a study of the deformation behaviour of a glassy phase in two Zr-based alloys, Zr65Ni10Cu5Al7.5Pd12.5 and Zr65Al7.5Ni10Pd17.5, performed in situ in a transmission electron microscope. In contrast to the case of shear localisation and formation of 10–20 nm thick shear bands in deformed bulk glassy samples studied earlier, it is found that in thin (electron-transparent) samples the glassy phase in front of a crack deforms more homogeneously and no nanocrystallisation takes place. The reasons for such behaviour are discussed. According to the observed results, one can conclude that the studied metallic glasses can be intrinsically ductile in submicrometre-sized volumes.

On the deformation and fracture behaviour of a Zr-based glassy alloy

The deformation behaviour of Zr60Cu16Ni14Al10 glassy alloy was found to exhibit cleavage-like fracture relief paired with typical vein patterns. The mirror-like cleavage area fraction is found to be comparable with that of vein areas. These two types of patterns alternate on the fracture surface in a direction normal to shear deformation. The structure of the studied alloy was characterised by X-ray diffractometry and scanning and transmission electron microscopy. A small volume fraction of crystals in the form of eutectic colonies were found here and there in the specimen. No distinct difference in the glassy structure of the cleavage-like fracture areas and the areas corresponding to vein patterns was found within the resolution of experimental techniques employed.

Synthesis and properties of Cu–Zr–Ag–Al glassy alloys with high glass-forming ability

New Cu–Zr-based glassy alloys with an unusual glass-forming ability (GFA) were synthesized in the Cu–Zr–Ag–Al system, based on a ternary Cu 45Zr 45Ag 10 alloy. The quaternary alloys exhibit large supercooled liquid region of 75–108 K and high-reduced glass transition temperature of 0.581–0.610. The best GFA was obtained for Cu 36Zr 48Ag 8Al 8 alloy, from which bulk glassy samples of up to 25 mm diameter were successfully fabricated by an injection mold casting method. The bulk glassy alloys exhibit high-compressive fracture strength of 1836–1981 MPa with plastic strain of 0.1–1.0% and excellent corrosion resistance in 1N H 2SO 4 solution.

Small-Scale Resistance Spot Welding of Zr Based Glassy Alloys

Resistance microwelding is an important joining process used in the fabrication of miniature instruments. The small-scale resistance spot weldability of Zr based glassy thin sheet alloys was investigated. Metallic glass sheets were successfully welded and amorphous structure was maintained in both weld nugget and heat affected zone. Joint strength that is evaluated by shear breaking force increased as the welding current increased, resulting from nugget growth. Fractured surface showed typical vein pattern.

Synthesis of Zr-Based Glassy Alloy Foams

The present basically concerns with the synthesis of foamy structured amorphous Zrbased alloy, Zr41.2Ti13.8Cu12.5Ni10.0Be22.5 (Vit-1), by liquid state processing. In this method, melt was injected in to the evacuated interstitial voids of the NaCl crystals placed in a copper mould. The casting has been subsequently washed with a jet of water to ensure the removal of NaCl entrapped in the casting, thus resulting in a porous structured casting. It shows the possibility of synthesizing amorphous metal foams with large dimensions using salt infiltration technique.

Crystallization behavior and consolidation of ball milled Zr 60Ti 5Ag 5Cu 12.5Ni 10Al 7.5 glassy powders

Zr 60Ti 5Ag 5Cu 12.5Ni 10Al 7.5 glassy powders produced by ball milling of crystalline compounds were consolidated by uniaxial hot pressing. The consolidation parameters were chosen in order to obtain partially crystallized bulk samples with a composite microstructure consisting of glassy, quasicrystalline and tetragonal CuZr 2 phases. Hardness measurements reveal promising mechanical properties: Vickers hardness of 4.61 GPa and estimated yield strength of 1.53 GPa. These values are comparable to those reported for bulk Zr-based glassy alloys prepared by other techniques.

Internal Friction of Nitrogen-Doped Zr-Based Glassy Composite Alloy

Internal friction of Zr-based glassy composite alloys containing dispersed-ZrN particles, which were prepared by a powder compact melting and liquid-quenching process using Zr-Al-Ni-Cu glassy alloy and AlN powders as the starting materials, has been investigated using a reed method over the temperature range of ∼90-350 K. It should be noted that a broad multi-composed peak was observed around 260 K. The peak internal friction was about 3 x 10 -3 . It was also noteworthy that the so-called AM effect of the Young's modulus in its temperature dependence was observed. In addition, the internal friction at the peak temperature depended little on the strain amplitude in the range of about ∼1 x 10 -6 -∼2 x 10 -4 . These results indicate that the observed internal friction peak is related to the relaxation process. Since the hydrogen content in the sample was very low (0.24 at%H), the observed internal friction peak is suggested to be induced by the interstitially doped nitrogen in the glassy phase.

Nanomechanical properties of embedded dendrite phase and its influence on inelastic deformation of Zr 55Al 10Ni 5Cu 30 glassy alloy

In order to study nanomechanical deformation property of an amorphous composite, nanoindentation and uniaxial compression tests were carried out on a dendrite containing Zr-based glassy alloy. Indenter penetration of the hard dendrite particle was about 100 nm shallower than that of the glassy matrix at the applied load 10 mN. Actual hardness, implying the load-supporting pile-up, of the dendrite phase was about eight times higher than that of the glassy matrix. Although this severe strength mismatch caused shear band bypassing and branching behaviors near the dendrite particles, ductility increment during the uniaxial compression test was negligible. The nil strengthening effects of the dendrite particle were discussed from the viewpoints of its small size, low volume fraction, sparse distribution and high cracking susceptibility of interface.

Process development of metallic glass wires by a groove quenching technique for production of coil springs

We have developed a continuous production process of metallic glassy alloy wires directly from melt. In the groove quenching process, Zr–Al–Cu–Ni alloy melt was injected to semi-circular groove located on upside surface of Cu-rotating disk. In an optimum operation condition, long glassy alloy wires with diameters ranging from 1 to 2 mm were produced. The cross-sectional geometry of the wires was nearly circular. The resultant wires exhibited almost the same thermal stability as that for the ribbon produced by a single roller melt spinning technique. The change in diameter was measured at an interval of each 10 mm. In addition, coil springs with a mean diameter of 7.2 mm could be formed using a viscous flow process. In this paper, the performance and properties of Zr-based glassy alloy wire are discussed.

Production of Glassy Coil Springs by Warm Coiling of Zr-based Glassy Alloy Wires

This study examines forming of coil springs from glassy alloy wires by warm coiling. Glassy Zr-Al-Ni-Cu alloy wires with a diameter of 1 mm were prepared by the rotating grooved-disk casting method and were wound round metal molds which were heated up to the supercooled liquid region of the alloy. Coil springs with mean diameters of 19 mm and 7.2 mm were formed by the warm coiling process. The coil springs formed within 1.8 ks in a temperature range between 673 K and 723 K maintained the glassy state, while the part heated for longer time in the coil spring formed at temperatures between 693 K and 743 K was crystallized. The spring constants of the coil springs measured by compressive test agree with the respective spring constant values calculated from the dimensions of the springs and the shear modulus of the alloy.

Evidence of icosahedral short-range order in Zr70Cu30 and Zr70Cu29Pd1 metallic glasses

Change in local atomic environment during crystallization of Zr-based glassy alloys was studied by extended x-ray absorption fine structure (EXAFS) spectroscopy. The formation of icosahedral quasicrystalline phase followed by crystallization of tetragonal CuZr2 has been observed in the Zr70Cu29Pd1 glassy alloy during annealing up to 850 K. On the other hand, the binary Zr70Cu30 alloy shows a single glassy to crystalline CuZr2 phase transformation. The local atomic environment of as-quenched Zr70Cu30 alloy is matched to an icosahedral local atomic configuration, which is similar to that of the as-quenched Zr70Cu29Pd1 alloy and the alloy annealed at 593 K containing icosahedral phase. Considering that the supercooled liquid region appears prior to crystallization in the Zr70Cu30 glassy alloy, the observed results support the theory claiming a strong correlation between the existence of local icosahedral short-range order and stability of the supercooled liquid state.