Zr-based Amorphous Alloys Research Articles

Effect of Pouring Temperature on Microstructure and Mechanical Properties of Zr-Based Amorphous Alloys

Amorphous alloys possess many excellent physical and chemical properties due to their unique atomic structure. However, owing to the high purity requirement, the production cost of amorphous alloys is often high. In this paper, Zr-based amorphous alloys were prepared from inexpensive industrial raw materials by the copper mold casting method. The effect of pouring temperature on the forming ability and mechanical properties of the alloys was investigated. The results show that at optimized pouring temperature, the glass forming ability as well as the mechanical properties of the alloys can be improved.

Strain dependence of diffusion in Zr-based bulk amorphous alloy

We evaluated the effect of strain on the diffusion process of amorphous alloys related to the strain mode in both as-cast and plastically deformed Zr-based bulk amorphous alloy. Experimental investigations of the diffusion process and the elemental distributions in the amorphous alloy were performed by secondary ion mass spectrometry after annealing at 523 K following 30% plastic deformation by multiple cold rolling. Mathematical modeling analyses show an inhomogeneous sequence of the diffusion process by effective strain. The compressive strain near the surface of the deformed amorphous alloy retards ∼13.7% of the diffusion process compared to the as-cast amorphous alloy. The combined experimental and mathematical analyses results reveal that the diffusion process of bulk amorphous alloys can be changed by strain variation and can be adjusted by controlling the effective strain during deformation.

On the crystallization kinetics of Zr–(Co,Ni)–Al bulk metallic glasses

Zr-based amorphous alloys are promising materials applied in engineering field, due to their strong glass-forming ability, outstanding mechanical properties and relatively low cost. In this work, the crystallization kinetics of Zr[Formula: see text]Co[Formula: see text]Ni[Formula: see text]Al[Formula: see text] ([Formula: see text], 2, 4 and 8; marked as Ni0, Ni2, Ni4 and Ni8, respectively) alloys are investigated in detail. The results show that, due to the addition of Ni, the glass transition of the alloys presents obvious dynamic characteristics, i.e., with the increasing heating rate, all characteristic temperatures are shifted to higher temperature. By fitting the Kissinger equation, the glass transition activation energy of Ni8 is the highest, indicating that Ni8 is much more difficult to crystallize. Therefore, the Ni8 alloy has the strongest anti-crystallization ability in the Zr[Formula: see text]Co[Formula: see text]Ni[Formula: see text]Al[Formula: see text] alloys investigated.

Nucleation and thermal stability of an icosahedral nanophase during the early crystallization stage in Zr-Co-Cu-Al metallic glasses

The early stage of crystallization in amorphous phases is a key step in the overall microstructural evolution. In a Zr-based amorphous alloy the formation of metastable nanophase was observed at the earliest crystallization stage, with an ultra-high nucleation density of 6.5 × 1024 m−3 and a size of ∼1–2 nm. The nanophase has an icosahedral structure and exhibits an extremely high thermal stability up to 150 K above the crystallization onset. The chemical and structural heterogeneity in the early stage of the glass crystallization were observed using high-resolution high-angle annular dark-field (HAADF) scanning transmission electron microscopy (STEM), which can be applied to study materials with atomic resolution. A nucleation kinetics analysis of the nanophase formation accounts for the high product number density and indicates a low interface energy value between the metastable clusters and the amorphous matrix, σa,i of 14 mJ/m2. The thermal stability and resistance to size change by growth or coarsening are attributed to a stalled growth due to solute depletion and the low σa,i value. With the high nucleation rate and the low barrier, it is remarkable that the kinetics follow conventional nucleation theory.

Conchoidal Fracture of Zr- and Mg-Based Amorphous Glass

In metallic glasses plastic deformation occurs via the creation and the propagation of a softened region in the shear bands. Some of the high strength metallic glasses (as Zr-based metallic alloys) exhibit complex shear band topography and the final failure respects the allocation of the shear bands. We studied the differences in the fracture surfaces of Zr-and Mg-based amorphous alloys. Ductile behaviour of the shear bands in Zr-based amorphous alloy tends to the dimple creation during the failure. On the fracture surfaces the vein pattern morphology manifestations were present. Conchoidal fracture was typical for Mg-based amorphous glass. Two different surface morphologies, plumes and rib marks ornament the fracture surfaces.

Characterization of nanoscale structural heterogeneity in an amorphous alloy by synchrotron small angle X-ray scattering

Amorphous alloys are the glassy solids that are formed through the glass transition of high-temperature melts. They therefore inherit the long-ranger disorders of melts and many quenched-in defects such as free volume. This inevitably leads to structural heterogeneity on a nanoscale that is believed to be as fertile sites for initiating relaxation and flow. However, due to limitations of spatiotemporal measurements, experimental characterization of the nanoscale structural heterogeneity in amorphous alloys has faced a great challenges. In this paper, an in-situ tensile testing setup with synchrotron small angle X-ray scattering is designed for a Zr-based (Vitreloy 1) amorphous alloy. By the small angle X-ray scattering, the structural heterogeneity of the Vitreloy 1 amorphous alloy can be described by the fluctuation of electron density. The small angle scattering images are recorded with the charge coupled device (CCD) detector, and then are azimuthally integrated into the one-dimensional scattering intensity curves using the FIT2D software. We apply the Porod law, Guinier law and Debye law to the obtained scattering intensity curves, and attempt to obtain the information about structural heterogeneity in the Vitreloy 1 amorphous alloy at different stress levels.The results indicate that the scattering intensity curve of the Vitreloy 1 amorphous alloy exhibits the positive deviation of Porod law. This observation proves that the amorphous alloy belongs to the non-ideal two-phase system, corresponding to the complicated spatial distribution between soft/liquid-like and hard/solid-like phases. According to the Porod's law, it is revealed that the diffuse interface exists between the two phases, associated with the density fluctuations in either of phases. Furthermore, we demonstrate that different scatterers coexist in the amorphous alloy and their characteristic sizes measured by the radius of gyration are mainly distributed between 0.8 nm and 1.6 nm. It deserves to note that the range of radii of gyration of scatterers are close to the equivalent sizes (1.3–1.9 nm) of shear transformation zones (STZs) for plastic flow in amorphous alloys. In addition, the shape of scatterer is far from a sphere, reminiscent of STZ activation regions of flat discs. It is therefore concluded that the scatterers with larger gyration radius correspond to the soft regions for the potential STZs, while those with smaller gyration radius correspond to the hard regions with lower free volume concentration. Finally, based on the correlation function defined by Debye, we analyze the correlation of electron density fluctuation between two arbitrary scatterers. The result indicates that the nanoscale scatterers in the amorphous alloy are strongly correlated only within a range of about 1 nm, which is consistent with the short-range ordered and long-range disordered structural features of the amorphous alloy. The image of the nanoscale heterogeneous structures characterized by the small angle X-ray scattering is almost not changed in the elastic deformation stage of the amorphous alloy. The present findings increase our understanding of the nanoscale structural heterogeneity in amorphous alloys, which is an important step to describe glass flow and relaxation.

Glass Forming Ability of Zr-Based Amorphous Alloys

Glass Forming Ability of Zr-Based Amorphous Alloys

Dynamic tensile deformation behavior of Zr-based amorphous alloy matrix composites reinforced with tungsten or tantalum fibers

Zr-based amorphous alloy matrix composites reinforced with tungsten (W) or tantalum (Ta) continuous fibers were fabricated by liquid pressing process. Their dynamic tensile properties were investigated in relation with microstructures and deformation mechanisms by using a split Hopkinson tension bar. The dynamic tensile test results indicated that the maximum strength of the W-fiber-reinforced composite (757 MPa) was much lower than the quasi-statically measured strength, whereas the Ta-fiber-reinforced composite showed very high maximum strength (2129 MPa). In the W-fiber-reinforced composite, the fracture abruptly occurred in perpendicular to the tensile direction because W fibers did not play a role in blocking cracks propagated from the amorphous matrix, thereby resulting in abrupt fracture within elastic range and consequent low tensile strength. The very high dynamic tensile strength of the Ta-fiber-reinforced composite could be explained by the presence of ductile Ta fibers in terms of mechanisms such as (1) interrupted propagation of cracks initiated in the amorphous matrix, (2) formation of lots of cracks in the amorphous matrix, and (3) sharing of loads and severe deformation (necking) of Ta fibers in cracked regions.

Corrosion behavior of amorphous Zr59Nb3Al10Ni8Cu20 alloy in aqueous HNO3 media

Purpose – The purpose of this paper was to investigate the corrosion behavior of the Zr59Nb3Al10Ni8Cu20 amorphous alloy in aqueous 1M, 6M and 11.5M HNO3 media using potentiodynamic polarization and weight loss determinations. Design/methodology/approach – The electrochemical study, weight loss analysis and surface investigation were carried out on amorphous Zr59Nb3Al10Ni8Cu20 alloy that had been immersed in aqueous HNO3 medium at room temperature to understand the corrosion behavior of Zr-based amorphous Zr59Nb3Al10Ni8Cu20 alloy. The amorphous state of the alloy was investigated using X-ray diffraction. Electrochemical studies were carried out in aqueous 1M, 6M and 11.5M HNO3 media by recording open circuit potential/time and potentiodynamic polarization characteristics. Optical microscopy and scanning electron microscopy were used to examine the surface morphology of the alloy after the electrochemical tests and weight loss determinations. Findings – The electrochemical results revealed that Ecorr values shifted toward more noble values, as the concentration of the nitric acid was increased, and this was attributed to the higher oxidizing power of the nitric acid. The higher value of corrosion current density was obtained for the Zr59Nb3Al10Ni8Cu20 amorphous alloy in aqueous 11.5M HNO3 medium at room temperature. The optical microscopy and scanning electron microscopy examinations revealed that the formation of protective oxide layer on the surface of amorphous Zr59Nb3Al10Ni8Cu20 alloy leads to the improvement in the corrosion behavior in nitric acid medium at room temperature. Originality/value – The results can be helpful in finding the suitable material for fuel reprocessing applications.

Correlation between Electrical Resistivity and the Structural Evolution of Zr-Based Bulk Amorphous Alloys

The electrical resistivity of three kinds of Zr-based bulk amorphous alloys as a function of continuous increasing temperature was measured by the direct current four-probe method. Combining with Differential scanning calorimetry (DSC) and X-ray diffraction (XRD) analysis, the correlation between the electrical resistivity and structural evolution of these amorphous alloys has been demonstrated. The experimental results showed that three amorphous alloys all had a small negative temperature coefficient of resistivity (TCR<-10-4 K-1) before crystallization. Little change of the electrical resistivity related with the glass transition process was observed, while the electrical resistivity decreased sharply once the crystallization occurred. The onset of crystallization determined by the electrical resistivity measurement was far lower than that by DSC. The different stages of crystallization behavior could be evidently identified by the change of the electrical resistivity.

Effects of dendrite size on dynamic tensile deformation behavior in Zr-based amorphous alloys containing ductile dendrites

In this study, dynamic tensile properties of Zr-based amorphous alloys whose dendrite size was varied with plate thickness (or cooling rate) were investigated, and effects of dendrite size on dynamic deformation mechanisms were verified. The dendrite size of the amorphous alloys was varied from 14.7μm to 42.8μm, while their volume fraction was almost constant. The dynamic tensile test results indicated that the ultimate tensile strength increased up to 2.6GPa because of strain rate hardening effect, whereas the elongation decreased to 1.1–1.6%, although the overall strength and elongation trends followed those of the quasi-static tensile test. According to the observation of dynamic tensile deformation behavior, the dendrite size greatly affected the dynamic tensile strength and elongation by the formation of deformation bands at dendrites, while dendrites themselves took over a considerable tensile load. However, the elongation was deteriorated when dendrites were large above a certain size level. In the alloy containing large dendrites, deformation bands were formed at dendrites in two intersected directions, but the amount of intersected deformation bands was reduced because deformation bands showed slip characteristics on a few slip planes of dendrite.

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.

Zr기지 비정질 합금 스크랩의 비정질 형성능 및 기계적 성질에 미치는 산소함량의 영향

Commercial Zr-based amorphous alloy was recycled and oxygen was introduced during the recycling process. The oxygen content can have a great effect on the glass forming ability and the mechanical properties of the alloy. Therefore, it was closely examined. The initial oxygen content in the raw material was 1,244 ppm. It was increased to 3,789 ppm in the alloy after ten recycling processes. As the recycling processes were repeated, the oxygen content increased. Specifically, after four recycling processes, it increased sharply as compared to that after three recycling processes. After ten recycling processes, the glass transition temperature (Tg) increased from 613 K to 634 K and the crystallization temperature (Tx) increased from 696 K to 706 K. On the other hand, the super-cooled liquid region (<TEX>${\Delta}T=Tx-Tg$</TEX>) decreased slightly from 83 K to 72 K while the reduced glass transition temperature (Trg = Tg/Tm) was 0.63, remaining constant even when the oxygen content was increased. These results indicated that the increased oxygen content deteriorated the glass forming ability. The bending strength as determined in a three-point bending test showed a sharp decrease from 3,055 to 2,062 MPa as the oxygen content was increased from 1,244 ppm to 3,789 ppm; the extension was also decreased from 3.02 to 1.74 mm. These findings meant that the alloy became brittle.

Plasticity enhancement in Ni–P amorphous alloy/Ni/Zr-based metallic glass composites with a sandwich structure

Using electrodeposition and chemical plating, Ni film and Ni–P film were coated on the surface of Zr-based amorphous alloy of Zr41.2Ti13.8Cu12.5Ni10Be22.5 (Vit.1). The compression behavior of the bare Vit.1 pillars and the Vit.1 pillars with the Ni-coating and Ni–P/Ni-coating was studied. The Ni–P/Ni/Vit.1 pillars with “amorphous–crystalline–amorphous” sandwiched structure formed a “hard–soft–hard” composite, and the Ni/Vit.1 pillars formed a “soft–hard” composite. The experimental results show that the surface coating increases the density of shear bands in the Vit.1 pillars, resulting in the improvement of the compression ductility. The Ni–P/Ni/Vit.1 pillars have the largest engineering plastic strain of 21.3±1.0% for the “uniform plastic deformation”, about 11.2 times of 1.9% of the bare Vit.1 pillars. The Ni–P/Ni-coating limits the propagation of shear bands, which leads to the initiation and formation of multiple shear bands. The technique developed in this work provides a new route to enhance the compression ductility of amorphous alloy at room temperature.

High-Temperature Sliding Wear Behavior of Zr-Based Bulk Amorphous Alloys

Bulk metallic glasses (BMGs) and their coatings are very attractive for tribological applications because of their high hardness. However, the frictional heat at the contact surfaces causes several effects such as oxidation, viscous flow, and nanocrystallization in the amorphous alloys. High-temperature wear testing offers an excellent way to characterize these effects and transitions in wear mechanisms. In this article, dry sliding wear behavior of the Zr-based BMG (Zr64.13Cu15.75Ni10.12Al10) is investigated in the temperature range of 293 K (room temperature) to 673 K. The wear surfaces showed indications of surface oxidation, viscous flow, formation of a protective layer, and abrasive wear, depending on the wear testing temperature. The Zr-based BMG exhibited the lowest wear rate of 9.7 × 10−4 mm3 m−1 associated with the formation of the protective surface layer at 473 K. With wear testing near glass transition temperature (574–673 K), the profuse crystallization of the surface seemed to change the wear mechanism to abrasive wear, resulting in the breaking of the protective layer and a high wear rate.

Determination of Al, Cu, Ni in Zr-Based Amorphous Alloy by Inductively Coupled Plasma Atomic Emission Spectrometry

A Method was studied for the determination of Al、Cu、Ni in Zr-based amorphous alloy by inductively coupled plasma atomic emission spectrometry (ICP-AES). Samples were dissolved by hydrochloric acid,nitric acid and hydrofluoric acid,analytical spectral lines for aluminum,copper,nickle are 308.215nm,327.396nm and 231.604nm.Interference of zinc was eliminated by the matrix-matching method, the experiments were done with optimized Operating Parameters. The correlation coefficients of the calibration curve are all 0.999,detection limits are 0.0010%,0.005% and 0.0006% respectively,and the range of recovery is 98%-104%.

Effects of a Zr-Based Bulk Metallic Glass on the &lt;i&gt;In Vitro&lt;/i&gt; Culture and Differentiation of Human Bone Marrow-Derived Mesenchymal Cells

The Zr-based bulk metallic glasses (BMGs) have excellent mechanical properties such as high strengths, low elastic moduli, and high hardness, can mitigate “stress shielding”effects and reduce the risk of “particle disease”.At the same time the Zr-based BMGs exhibit good corrosion resistance in a physiologically relevant environment. These properties provide a good opportunity for potential biomedical applications. In this article, the effects of a Zr-based amorphous alloy (Zr60.5Al8.9Fe10.2Cu10.2Ag9.7Ti0.5) on the in vitro culture and induced differentiation of human bone marrow-derived mesenchymal stem cells (hMSCs) are studied and in conclusion that Zr-based BMGs have a significant advantage in the human bone implant material for good biocompatibility.

Zr 기지 비정질 합금 스크랩의 비정질 형성능 및 기계적 성질에 미치는 재용해 횟수와 탄소 함량의 영향

A commercially used Zr-based amorphous alloy was recycled and the effects of introducing carbon during recycling on the glass forming ability and mechanical properties of the alloy were investigated. The initial carbon content used in this study was 229ppm. The carbon content was gradually increased as the number of recycling iterations was increased and after the <TEX>$4^{th}$</TEX> recycling it rapidly increased. As return scrap was recycled, polygonal particles precipitated, and they were identified as ZrC. The amount of the precipitates also increased with recycling. Tg, Tx and <TEX>${\Delta}T$</TEX> of the base alloy were 615 K, 696 K and 81 Kr respectively and they changed to 634 K, 706 K and 72 K after the <TEX>$10^{th}$</TEX> recycling. The decrease of the <TEX>${\Delta}T$</TEX> value indicates deterioration of the glass forming ability. Hardness was not changed during three iterations of recycling but after the <TEX>$4^{th}$</TEX> recycling it significantly increased. This is ascribed to an increase of amount of the hard particles, namely ZrC.

Effect of cast process and microalloying on the fracture toughness of Zr-based bulk amorphous alloys

In order to clarify the effects of tilt- or suction-cast processing and microalloying of minor Si on the three-point bending fracture toughness of the Zr-based bulk metallic glasses (BMGs), the tilt-cast and suction-cast Zr53-based and Zr48-based BMGs with and without Si were studied. The results revealed that the tilt-cast specimens present much better fracture toughness than the suction-cast counterparts as a result of their lower degrees of residual porosity. In addition, the microalloying of Si to 0.75at.% in these BMGs would impose negative effects on their fracture toughness. The highest fracture toughness of 120MPam was achieved for the tilt-cast Zr53Cu30Ni9Al8. Moreover, the morphology of fracture surface, the calculated fracture energy, and the Poisson’s ratio show the similar trend to prove that the tilt-cast Zr-53 BMG without Si possesses the best fracture toughness among these BMGs in this study.

Zr-based 비정질 합금의 비정질 특성에 미치는 Sn의 영향

Zr-based 비정질 합금의 비정질 특성에 미치는 Sn의 영향