Zr-based Alloys Research Articles

Electrochemical micromachining of ZrCu-based amorphous alloy in ethylene glycol solution

Their excellent physical, chemical, and mechanical properties give ZrCu-based amorphous alloys a wide range of application prospects as advanced functional and structural materials for military and aerospace uses and in precision devices. Micro-electrochemical technology has been used to process amorphous alloys, and this paper reports the wire electrochemical micro-machining (WECMM) of the Zr67Cu15Ni11Al4Ti3 amorphous alloy. The dissolution characteristics and processing of the alloy in aqueous solutions are analyzed to understand the WECMM of this ZrCu-based amorphous alloy. Unlike with Cu-free Zr-based amorphous alloys, the Cu in the present case is electrolyzed quickly and generates a large amount of product deposition on the surface of the cathode after it is ionized, thereby seriously hindering the processing. Unlike the pure charge-transfer control process in an aqueous solution, the polarization process of the alloy in a glycol solution is controlled by both charge transfer and diffusion. In a glycol solution, the two-phase electric double layer comprises a compact layer and a diffusion layer, ions move relatively slowly between the cathode and anode, and products form relatively slowly. This is effective in (i) strengthening the reverse electric field effect of the bipolar pulse, (ii) hindering the migration of cations to the cathode, and (iii) directly avoiding the formation of products, thereby allowing the formation of high-quality micro-structures of ZrCu-based amorphous alloy with a relatively large thickness of 550 μm.

Irradiation resistance of chromium coatings for ATFC in the temperature range 300–550°C

Within the accident tolerant fuel cladding (ATFC) concept, chromium coatings appear to be promising for protecting zirconium alloys from high temperature oxidation. The effects of high energy heavy ion irradiation in the temperature range of 300–550°C on the structure of chromium coatings deposited on Zr-based (E110) alloy substrate by the cathodic arc evaporation method were studied. Isotropic growth of the grain size in chromium coatings from the initial 250 nm to 476 nm at 550°C is caused by irradiation with 1.4 MeV argon ions to the dose of 25 displacements per atom (dpa). Maximum swelling up to 1.6 % was observed under the irradiation temperature of 500°C.

APT characterization and modeling of irradiation-induced Nb-rich nanoclustering in Zr-1.0%Nb alloys

Recent development of Zr-based alloys containing Nb solutes have demonstrated promising improvements in corrosion resistance and reduced irradiation growth, particularly when irradiation-induced Nb-rich nanoclusters are present and inhibit 〈c〉 loop formation. In this study, a Zr-1.0%Nb alloy is irradiated with either Kr2+ ions or neutrons to 5 dpa at 310 °C. Using atom probe tomography, radiation-induced Nb-rich nanoclusters and a corresponding reduction of Nb matrix composition from 0.40 at% to 0.26 at% and 0.34 at% is characterized following each irradiation, respectively, suggesting that matrix solutes coalesce to form nanoclusters. Irradiation with Kr2+ ions induces nanoclusters that are larger and denser than those following neutron irradiation. Utilization of a simple rate-theory nanocluster evolution model demonstrates high sensitivity to the solute migration, vacancy formation, and vacancy migration energies directly influencing radiation-enhanced mobility of solutes, enabling exploration of irradiation temperature effects and potential differences in nanocluster evolution for different solutes or alloy systems.

Improvement in the hydrothermal corrosion resistance of Ti-based nitride coatings by adding Cr for accident tolerant fuel cladding applications

In order to improve the hydrothermal corrosion resistance of nuclear fuel cladding, TiN and TiCrN were deposited on the surface of a Zr-based alloy tube as an environmental barrier coating using arc ion plating and DC sputtering under an Ar+N2 atmosphere. A hydrothermal corrosion test was carried out at 360 °C and 20 MPa for 120 days in simulated PWR primary water chemistry. To similar the water chemistry, 1200 ppm H3BO3, 2.2 ppm LiOH, and 25 cc·H2/kg·H2O were added to pressurized water. The pH and conductivity were controlled to be 23 μS/cm and 6.5, respectively. After the hydrothermal corrosion test, a microscale of FeTiO3 covered the entire surface of TiN due to its rapid corrosion rate. On the other hand, the thickness of the oxide layer on TiCrN was reduced to a range of tens of nanometers. The corrosion product on the surface was identified as FeCr2O4. This spinel-structured FeCr2O4 effectively suppressed the corrosion of the TiCrN and improved the corrosion resistance.

Current Research Status on Cold Sprayed Amorphous Alloy Coatings: A Review

Compared with traditional crystalline materials, amorphous alloys have excellent corrosion and wear resistance and high elastic modulus, due to their unique short-range ordered and long-range disordered atomic arrangement as well as absence of defects, such as grain boundaries and dislocations. Owing to the limitation of the bulk size of amorphous alloys as structural materials, the application as functional coatings can widely extend their use in various engineering fields. This review first briefly introduces the problems involved during high temperature preparation processes of amorphous coatings, including laser cladding and thermal spraying. Cold spray (CS) is characterized by a low-temperature solid-state deposition, and thus the oxidation and crystallization related with a high temperature environment can be avoided during the formation of coatings. Therefore, CS has unique advantages in the preparation of fully amorphous alloy coatings. The research status of Fe-, Al-, Ni-, and Zr-based amorphous alloy coatings and amorphous composite coatings are reviewed. The influence of CS process parameters, and powders and substrate conditions on the microstructure, hardness, as well as wear and corrosion resistance of amorphous coatings is analyzed. Meanwhile, the deposition mechanism of amorphous alloy coatings is discussed by simulation and experiment. Finally, the key issues involved in the preparation of amorphous alloy coatings via CS technology are summarized, and the future development is also being prospected.

Effect of Ti addition on properties of Zr54Al10.2Ni9.4Cu26.4 glass forming alloy

(Zr54Al10.2Ni9.4Cu26.4)100−xTix (x = 0–0.5, at%) bulk metallic glasses were prepared by water-cooled copper suction casting method. The Ti microalloying effect on glass forming ability and physical and chemical properties of Zr54Al10.2Ni9.4Cu26.4 glass forming alloy were systematically investigated. The glass forming ability is the largest for the Zr-based alloy with 0.3 at% Ti. The glass transition temperature is decreased by the Ti addition, while the supercooled liquid region is broadened. Both strength and plasticity are significantly enhanced by the Ti addition. The yield strength and the fracture strength firstly increase and then decrease when the Ti content reaches up to 0.3 at%. The plastic strain and the fracture strain increase with increasing Ti content. In addition, the corrosion potential is slightly decreased by the Ti addition. The corrosion current density increases with increasing Ti content. The pitting corrosion becomes increasingly serious with increasing Ti content. The honeycomb corrossion structure can be clearly observed when the Ti content reaches up to 0.5 at%. The corresponding mechanisms are also discussed in detail.

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.

Effect of cooling rate on fluidity and glass-forming ability of Zr-based amorphous alloys using different molds

Herein, the effect of cooling rate on fluidity and glass-forming ability (GFA) of the Zr41.2Ti13.8Cu12.5Ni10Be22.5 amorphous alloy is systematically studied by using a self-designed fluidity testing system and gravity casting. The molds are made of refractory steel, purity graphite and copper with spiral cavities. Moreover, the fluidity model of amorphous alloy is established and flow length is calculated based on the heat balance theory. Furthermore, the fluidity of amorphous alloy melt is quantitatively and qualitatively analyzed by comparing the calculated and experimentally measured flow lengths. The results reveal that the cooling capacity of mold mainly influences the flow length of amorphous alloy melt. Moreover, the discrepancy between experimentally measured and theoretically calculated flow lengths can be ascribed to the difference between actual and theoretical thermophysical parameters. X-ray diffraction (XRD), differential scanning calorimetry (DSC) and high-resolution transmission electron microscopy (HRTEM) reveal the traces of crystalline phase in samples prepared using steel and graphite molds, however, the crystalline phase is not observed in the case of copper mold. The results demonstrate that the mold material renders a certain influence on GFA of Zr41.2Ti13.8Cu12.5Ni10Be22.5 amorphous alloy.

Effect on microstructure and plastic deformation behavior of a Zr-based amorphous alloy by cooling rate control

In this study, Zr41.2Ti13.8Cu12.5Ni10Be22.5 amorphous alloys samples with the same diameter (8 mm) were prepared by using self-designed molds (viz. refractory steel, pure graphite, and copper molds) with different cooling capacities. Moreover, by eliminating the size effect, the effect of the cooling rate on the microstructure and compression deformation behavior of Zr41.2Ti13.8Cu12.5Ni10Be22.5 amorphous alloys was investigated. Differentiation of the cooling curves revealed that the instantaneous cooling rates of the alloy melt at the glass transition temperature (Tg) are 45, 52, and 64 K·s―1 for refractory steel, pure graphite, and copper molds, respectively. X-ray diffraction, differential scanning calorimetry, and high-resolution transmission electron microscopy analysis revealed that with the decrease in the cooling rate, trace icosahedral-like atomic clusters and nanocrystals appear in local areas of the amorphous alloy and that the amount of free volume decreases with the increase in the amount of icosahedra-like atomic clusters and nanocrystals. Compression test results revealed that the elastic strain, yield strength, and compressive strength of the amorphous alloy marginally change with the decrease in the cooling rate, while the plastic strain gradually increases. By fitting, the effective size of the vein-like pattern was linearly related to the enthalpy released during structural relaxation and plastic strain, indicating that at a low cooling rate, the trace nanocrystals in the amorphous alloy could not effectively improve its plasticity and that the amount of free volume mainly affects its plasticity.

Phase equilibria thermodynamics and solidified microstructure in the Ag-Cr-Zr system

Ag-Cr-Zr alloy is a promising Zr-based alloy with excellent strength and hardness. Lack of investigations on phase equilibria and solidified microstructure of the Ag-Cr-Zr system limits the design of high-performance Zr-based alloys. Solidified microstructure and phase transition temperature in the Ag-Cr-Zr system are experimentally investigated using scanning electron microscopy, electron probe microanalysis, X-ray diffraction, and differential scanning calorimetry. The microstructure of the ca-cast Ag-Cr-Zr is investigated in detail, and a liquid miscibility gap extending from Ag-Cr binary system is measured. The phase transition temperatures along three vertical sections are determined. Based on these experimental results and critical literature review, a thermodynamic modeling of the Ag-Cr and Ag-Cr-Zr systems was constructed by CALPHAD method, and the calculated phase diagram is in accordance with the experimental data. Besides, the Scheil solidification is simulated and the simulated results agree with the observed solidified microstructure. The reaction scheme for the whole Ag-Cr-Zr ternary system is calculated for the first time. This work not only fills in the gap in the thermodynamic description of the Ag-Cr-Zr system, but also provides a hybrid approach of thermodynamic calculations and key experiments for the sake of obtaining the desired solidified microstructure.

Effect of Hydrogen Pressure in the Stage of Recombination of HDDR Process on Phase Equilibrium in Nd – Fe – Co – B – Zr-Base Alloys

X-ray diffractometry with mathematical processing of the diffraction patterns by the Tikhonov method of regularization, which enhances the resolution, is used to study the phase state in Nd – Fe – Co – B – Zr-base alloys during the reverse reaction of HDDR process at different hydrogen pressures. The range of hydrogen pressures in which the reverse reaction (recombination) of the HDDR process develops fully is determined experimentally.

Effect of pH and NaF addition on corrosion of Zr-based bulk metallic glass in Na2SO4-containing solution

In order to expand the application of Zr-based bulk metallic glasses (BMGs) in the field of biomaterials, it is vital to investigate their corrosion behaviour in different solution environments. However, until now, the corrosion behaviour of Zr-based BMGs in F−-containing solution has been rarely studied, and the corrosion mechanism is not fully understood. In this study, the effect of pH and NaF addition on the corrosion behaviour of Zr52Al10Ni6Cu32 BMG in Na2SO4-containing solution has been investigated by employing the standard electrochemical methods. The relationship between the critical pF value and pH has been subsequently obtained, which provides a criterion for judging the state of corrosion of Zr-based BMGs in F−-containing solution. The cathodic reaction mainly involves the reduction of the dissolved oxygen in the solution, and the kinetic mechanism is similar to that of pure Zr. An oxidation peak appearing during the upward polarization scanning is attributed to the active dissolution of Cu caused by SO42− and F−. During upward polarization, different pH values and addition of NaF are observed to result in consequent film breakdown behaviour. For 0.1 M NaF and pH = 8.0, the protective ZrO2 passive film is noted to be replaced by the corrosion product of the Zr–F compound. However, at pH = 4.0 with 0.001 M NaF, the F− concentration is not sufficient to form the Zr–F corrosion products, and the dissolution rate of the passive film is enhanced due to the reduced pH. This study provides a deeper understanding of the corrosion mechanism of Zr-based BMGs alloys in F−-containing solution.

Novel Biocompatible Zr-Based Alloy with Low Young's Modulus and Magnetic Susceptibility for Biomedical Implants.

The microstructure, mechanical properties, magnetic susceptibility, electrochemical corrosion performance, in vitro cell compatibility and blood consistency of Zr-16Nb-xTi (x = 0, 4, 8, 12 and 16 wt.%) materials were investigated as potential materials for biomedical implants. X-ray diffraction (XRD) and Transmission electron microscopy (TEM) analyses revealed the secondary phase martensite α’ formed during the quenching process. The phase composition contained metastable β and martensite α’, resulting from Ti addition. These phase constitutions were the main causes of a low Young’s modulus and magnetic susceptibility. The in vitro cytocompatibility analysis illustrated that the MG63 cells maintained high activity (from 91% to 97%) after culturing in Zr-16Nb-xTi extraction media for 12 days due to the high internal biocompatibility of Zr, Nb and Ti elements, as well as the optimal corrosion resistance of Zr-16Nb-xTi. On the basis of Inductively coupled plasma optical emission spectrometry (ICP-OES) ion release studies, the concentration of Zr, Nb and Ti was noted to reach the equipment detective limit of 0.001 mg/L, which was much lower than pure Ti. With respect to the corrosion behavior in Hank’s solution, Zr-16Nb-16Ti displayed superior properties, possessing the lowest corrosion current density and widest passivation region, attributed to the addition of Ti. The blood compatibility test illustrated that the Zr-16Nb-xTi materials were nonhemolytic, and the platelets maintained a spherical shape, with no aggregation or activation on Zr-16Nb-xTi. Overall, Ti addition has obvious effects on the developed Zr-16Nb-xTi alloys, and Zr-16Nb-4Ti exhibited low magnetic susceptibility, low modulus, good biocompatibility and proper corrosion properties, demonstrating the potential of use as implant biomaterials.

Effects of Alloying Additions on the Glass Forming Ability and Corrosion Resistance of Bulk Zr-Based Amorphous Alloys

By using the real-place Recursion method,the effects of alloying additions (Nb, Ta, Y, La) on glass forming ability(GFA) and corrosion resistance of bulk Zr-based amorphous alloys are studied. An atomic group model in the Zr2Ni primary crystalline phase centered to Ni atom are constructed by computer programming. We have calculated the total bond order integral (£BOI) between Ni atom and its neighbor elements (Nb, Ta, Y, La), also calculated the Fermi energy level of alloying elements. The calculation results show that the XBOI and the glass forming ability are greatly enhanced after Y substitution. Nb, Ta, La decrease the GFA and La has little influence on the GFA of the alloys.Nb, Y, La enable Zr-based amorphous easy to passive and increase corrosion resistance. Therefore, Y and La are most effective on glass forming ability and corrosion resistance of Zr-based amorphous alloys. By addition of minor Y and La can produce the new bulk amorphous alloys with good corrosion resistance.

Experimental Verification of Phase Diagram Calculations of Zr-Based Alloys after High-Temperature Oxidation

Zirconium-based alloys are commonly used as a material for nuclear fuel claddings in the light water reactors. The cladding material must function to fix a huge number of pellets, while conducting heat into the coolant that flows turbulently around the fuel rods. Cladding tubes can contain gaseous fission products that escape the fuel. Thus, by functioning as a sealed unit, it prevents a contamination of the coolant water with high-radioactive fission products. The integrity of claddings is always a critical issue during reactor operation and wet or dry storage and transport of the spent fuel rods. Moreover, the role gains importance at Loss of Coolant Accidents (LOCA). After Fukushima accident, cladding materials are widely studied with the purpose to reduce the high-temperature oxidation rate and enhance accident tolerance. In our contribution, we introduce the studies on Zr-1Nb (E110) cladding tubes after high-temperature steam oxidation at 1350 °C. During the testing of claddings, microscopy analytical methods play an important role in experimental verification of pseudo-binary phase diagram Zr1Nb-O, i. e. particularly in oxygen content determination at phase transitions. Wave Dispersive Spectroscopy (WDS) with complementary nano-indentation method were used to characterize the Zr1Nb microstructure formed after LOCA. It includes the regions from an oxide and oxygen-stabilized α-Zr(O) to the acicular prior β-Zr phase. The decrease of hardness and Young's modulus corresponds with oxygen content measured in line-profiles by WDS. The oxygen level at transition points was partly determined from Fe, Nb β-stabilizers and significant change in mechanical properties in fine-grained prior β-Zr. The slight fluctuation of oxygen values in adjacent grains can be caused by preferential oxidation through the favorably oriented α-Zr(O) grains studied by WDS+EBSD. As well, the non-uniform oxygen-rich α-Zr(O) phase adjacent to the oxide was characterized by EBSD & WDS. Increasing hydrogen content in specimens, 10, 700 and 1000 ppm H, caused increasing solubility of oxygen in prior β-Zr phase upon high-temperature and the cladding material hardening.

Study on the variation of properties of Cu–Cr–Zr alloy by different rolling and aging sequence

The relationship between rolling-aging sequence and the microstructure evolution, mechanical-electrical properties of hot rolled-quenched Cu-0.67Cr-0.27Zr-0.12Ni-0.03Si-0.04Ti alloy was investigated in details and the underlying mechanism of the abnormal decrease in electrical conductivity of the peak-aged alloy by cold rolling was also revealed. The results indicated that a good combination of the tensile strength (585.5 MPa), yield strength (562.1 MPa), Vickers hardness (197.6 HV), and electrical conductivity (67.4 %IACS) was obtained in the Cu–Cr–Zr-based alloy by a sequence of peak aging at 450 °C for 2 h followed by 80% room-temperature rolling and then secondary aging at 400 °C for 1 h. Compared with the rolling-aging process, the strength improvement of the alloy by the aging-rolling-aging process was mainly dominated by dislocation density strengthening. Additionally, a decrease in electrical conductivity of the peak-aged alloy after cold rolling was attributed to the re-dissolution and the refinement of partial coherent precipitates.

Structural mechanism of glass forming ability in Zr-based binary alloys

This study presents a computational framework to investigate the structural mechanism of glass forming ability (GFA) by carefully comparing two model systems of Zr-based binary metallic glasses (MGs) with distinct GFAs, Zr2Cu and Zr2Ni. Based on the Voronoi diagram of three-dimensional spherical atoms, the free volume, the cluster regularity, and the atomic packing efficiency in the atomic structure of Zr2Cu and Zr2Ni MGs are efficiently and accurately calculated as a function of temperature during quenching from melts to MGs. The glass transitions were found to occur with the fractional free volume reaching a seemingly universal value at ∼2%–3%. Although the glass states of both MGs show very similar linear temperature-dependent behavior, their supercooled liquid states behave quite differently, e.g., the structure of Zr2Cu changes much faster than that of Zr2Ni, and by extrapolating the temperature dependence of the free volume of liquids, the free-volume could quickly vanish in the Zr2Cu supercooled liquid at ∼210 K, while it remains even down to 0 K in Zr2Ni. In addition, Zr2Cu has higher atomic packing density and cluster regularity at low temperature region, also is more spatially homogeneous than Zr2Ni. These results reveal clear structure characteristics which are associated with the viscosity of the supercooled liquids and the Gibbs energy of glass states, therefore, the GFA and stability of MGs.

Microstructures of the bonding area in laser cladded Zr-based amorphous alloy coating on magnesium

The Zr65Al7.5Ni10Cu17.5 amorphous alloy was laser cladded on magnesium substrates by employing a 5 kW continuous wave CO2 laser. The laser scan rate ranged from 3 to 10 mm/s and the laser output power ranged from 2000 to 4000 W. The typical microstructures in the bonding area of specimens at a scan rate of 3 mm/s or 5 mm/s consist of white Zr rich particles, grayish Mg rich eutectics and gray Mg rich equiaxed dendrites, while a characteristic sharp interface was obtained at a scan rate of 10 mm/s. Neither obvious micro-voids nor porosity is observed in this area, implying a good bonding condition, In addition to the structural features of the microstructure, the resulted molten depth of the substrate upon different scan rate and the laser output power during the bonding process were also investigated to build to a more comprehensive connection between the process conditions and the bonding properties. The growth type of the Mg rich phase in the bonding area was analyzed by using Hunt’s CET model and KGT model and the results showed a good agreement with the experimental results.

High-throughput development and applications of the compositional mechanical property map of the β titanium alloys

By a combination of the nanoindentation and electron probe microanalysis (EPMA) techniques, the traditional diffusion couple technique is extended to map the mechanical property of β-type Ti alloys over a wide composition range, which can be utilized to develop very versatile novel bio-Ti alloys for hard tissue replacements in artificial bones, joints, and dental implants. To create complete single-phase composition ranges of Ti-based bcc solid solution, 12 types of bcc Ti–Nb–Zr–Mo/Ti–Nb–Zr–Ta quaternary diffusion couples were fabricated and annealed at 1273 K for 25 h. In this way, the composition-mechanical property relationships in the vast composition space of Ti-based alloys were established using EPMA and nanoindentation probes. Notably, the measured composition-dependent Young's moduli, hardness, and elastic recovery as well as the derived ratio of hardness to Young's modulus, and the ratio of the cube of hardness to the square of Young's modulus, in the developed compositional mechanical property database, were visualized in a five-dimensional scatter plot. This enables an effective tool to screen the Ti–Nb–Zr-based alloys for orthopedic and dental applications according to different clinical requirements, and to rationalize the fundamental mechanical relationships in the rapid development of β-Ti alloys.

Quantitative characteristics of shear bands formed upon deformation in bulk amorphous Zr-based alloy

The quantitative characteristics of steps formed by shear bands (SB) on the surface of deformed samples of bulk amorphous Zr60Ti2Nb2Cu18.5Ni7.5Al10 alloy were studied after high pressure torsion (HPT) and after rolling. It was found that the SB design depends on deformation mode. The deformation value decisively affects the SB power (the step height).