Zr Powders Research Articles

Microstructure and Properties of ZrB2-SiC Reinforced Copper Matrix Composite Coatings Prepared by Laser Cladding.

With the use of electrolytic Cu powder, Zr powder, Si powder and nickel-coated B4C powder as cladding powders, in-situ synthesized ZrB2-SiC reinforced copper matrix composite coatings were prepared by laser cladding on the surface of the copper substrate to improve the surface hardness and wear resistance. Under the condition of a laser energy density at 60 kJ/cm2, the macroscopic surface of the composite coating was continuously flat. The microstructure and phase of the cladding coating were analyzed by means of XRD and SEM. The reinforcements with nano-scale particle and micron-scale needle-like structures were in-situ synthesized in the cladding coating, and the content of the reinforcement phase decreased slightly from the coating surface to the substrate. The phase analysis results showed that the reinforcements included ZrB2 and SiC. When the content of the reinforcement was increased to 30 wt%, microhardness also increased from 48 HV0.2 to 309 HV0.2, which was about 5.6 times that of the copper matrix. The wear resistance of the composite coatings was characterized by current-carrying wear tests. By keeping the sliding speed and load constant, the wear rate decreased with an increase in the reinforcement content, and the wear mechanism changed from adhesive wear to abrasive wear. The wear rate of the composite coating with the current was higher than that without the current due to its electric ablation and high temperature.

Synthesis of MAX phase-based ceramics from early transition metal hydride powders

MAX phase ceramics are typically prepared by the reactive sintering of elemental powders that are often coarse, expensive, and prone to oxidation. The temperature-driven dehydrogenation of metal hydride powders offers an alternative synthesis approach, as the hydrides decompose into phase-pure, dimensionally fine elemental powder particles. The increased reactivity of these in situ formed, fine powder particles drastically reduces the formation temperature of the antecedent intermetallic phases, without forming excess binary carbides or facilitating powder oxidation in the Ti-Al-C and Zr-Al-C systems. This work elucidates the effect of metal hydrides on the sequence of formation reactions in MAX phase ceramics. In the Zr-Al-C system, the use of coarse, oxidation-prone elemental Zr powders prevented MAX phase formation, whereas spark plasma sintering of ZrH2 powders at 1500 °C produced ceramics containing 60 wt% Zr3AlC2. Similarly, in the Ti-Al-C system, spark plasma sintering of TiH2 powders at 1200 °C produced phase-pure Ti3AlC2 ceramics.

Nanocrystalline ZrC coated graphite and its effect on mechanical properties and thermal shock resistance of low-carbon Al2O3–C refractories

Nanocrystalline ZrC coated graphite was synthesized in mixed molten salt system, and the effect of different zirconium sources and reaction temperature on its synthesis was studied. The effects of nanocrystalline ZrC coated graphite on the microstructure, thermal shock resistance and cold mechanical properties of low-carbon Al2O3–C refractories in different atmospheres were studied. The results indicated that nanocrystalline ZrC coated graphite synthesized by Zr powder had a more uniform coating structure than ZrO2 as a zirconium source, and increasing the reaction temperature was beneficial for the synthesis of ZrC. The sample with nanocrystalline ZrC coated graphite fired in nitrogen atmosphere had better mechanical properties, the cold modulus of rupture was 15.67% and 50.67% higher than that of the samples fired under argon atmosphere and carbon-embedded atmosphere, respectively. Meanwhile, Sialon played a significant role in improving the mechanical properties of the samples after thermal shock. In addition, the treatment in argon or carbon-embedded atmosphere was beneficial in improving the thermal shock resistance of the samples.

Effect of oxide dispersoids on precipitation-strengthened Al-1.7Zr (wt %) alloys produced by laser powder-bed fusion

Binary Al-1.7 wt % Zr (Al-0.5 at % Zr) alloys, with and without 1 wt % (0.7 vol %) Al2O3 nanoparticle additions (80–100 nm), are fabricated by laser powder-bed fusion (L-PBF) from blends of Al, Zr, and Al2O3 powders. Elemental Zr, which is ~80 % dissolved in the melt pool, forms primary L12-Al3Zr precipitates upon solidification and is also retained in a supersaturated solid solution in the Al matrix. The primary L12-Al3Zr phase takes three forms: (i) discrete, micron-sized precipitates that nucleate fine Al matrix grains, (ii) elongated “strings” of submicron precipitates forming in highly enriched Zr regions, and (iii) < 100 nm precipitates within fine Al-grains. The Al2O3 nanodispersoid additions are either lost to slag or entrapped within Al-grains as oxide dispersoids, resulting in an oxide concentration of 0.46 wt % for the modified ODS alloy. Al2O3 nanoscale dispersoids (0.28 wt %) are also observed in the unmodified alloy, and are assumed to originate from (i) native oxides from the surface of the Al powder particles, and/or (ii) reaction with trace amounts of oxygen in the processing environment. The hardness upon aging at 400 °C reaches a peak value of ~750–850 MPa after 1.5 h, consistent with precipitation of secondary L12-Al3Zr nanoprecipitates. Upon overaging, hardness slowly decreases to 500 MPa (the as-processed value) after 1,500 h at 400 °C, with no difference observed between the Al-Zr and Al-Zr-Al2O3 alloys. Strengthening mechanisms combines Hall-Petch strengthening from micron-sized grains, Zr solid-solution strengthening, and secondary L12-Al3Zr precipitate strengthening, with slow precipitate coarsening and effective grain pinning by Al3Zr precipitates and oxide dispersoids located at grain boundaries. Creep resistance is comparable for both alloys, which show threshold stresses of ~15 and 6 MPa, at 300 and 400 °C respectively. Oxygen content analysis is recommended for all Al-based alloys fabricated via L-PBF due to the potential for non-reproducible nanoscale oxide inclusions (from native oxide on Al powders and from reaction with residual oxygen), which may affect the mechanical properties of the alloys, but are difficult to observe via SEM or TEM analysis.

Operando X-ray diffraction study of thermal and phase evolution during laser powder bed fusion of Al-Sc-Zr elemental powder blends

Elemental powder blends are an emerging alternative to prealloyed powders for high-throughput alloy design via additive manufacturing techniques. Elemental Al+Sc(+Zr) powder blends were processed by laser powder bed fusion into Al-Sc and Al-Sc-Zr alloys, with operando X-ray diffraction at the Swiss Light Source extracting the structural and thermal history of the process. The pure Sc and Zr particles were found to react with the molten Al pool at 550–650 °C, well below their respective melting temperatures. Various scan areas (1 × 1, 2 × 2, 4 × 4, and 8 × 2 mm 2 ) were studied to compare (i) the base plate “preheating” effect caused by prior laser scans, (ii) the return temperature reached after the melting scan and before the following scan, (iii) the initial cooling rate immediately after solidification, and (iv) the time spent in the “intrinsic heat treatment range”, defined as 300–650 °C, where secondary Al 3 (Sc,Zr) precipitation occurs. Microstructural analysis of the as-built samples show 110–140 nm L1 2 -Al 3 (Sc,Zr) primary precipitates at the bottom of the melt pool. The 1 × 1 mm 2 samples exhibit the most elongated grains (long axis of 10 ± 5 µm), which correlates with the highest build plate temperature and the slowest initial cooling rate (3–5 × 10 5 K/s). In comparison, the 4 × 4 mm 2 samples exhibit the smallest equiaxed grains (2 ± 0.6 µm), corresponding to the lowest build plate temperature and the fastest initial cooling rate (6–7 × 10 5 K/s). These results indicate the need for establishing a minimum feature size during part design, or for modifying the laser parameters during processing, to mitigate microstructure and performance differences across features of different sizes.

Mechanisms responsible for enhancing low‐temperature oxidation resistance of nonstoichiometric (Zr,Ti)C

AbstractA series of (Zr,Ti)Cx (x = 0.7–1.0) samples were fabricated by a modified spark plasma sintering apparatus to investigate the effects of carbon concentration and Ti substitutions on the oxidation behavior. Crushed powders of (Zr,Ti)Cx were oxidized in lab air (N2–20‐vol.% O2) from room temperature to 900°C. The results indicated that Zr0.8Ti0.2C0.8, with a nominal carbon concentration x = 0.8, displayed good oxidation resistance, which was attributed to the formation of dense t‐(Zr,Ti)O2 oxide solid solution. During the oxidation of (Zr,Ti)Cx, Ti substitutions for Zr enhanced the outward diffusion of carbon, enabling a uniform carbon layer and a Zr–Ti–C–O layer on the surface of carbides. The formed carbon layer improved the oxidation resistance of (Zr,Ti)Cx below 550°C, where carbon is relatively oxidation resistant. Increasing the Ti concentration was found to enhance the oxidation resistance of (Zr,Ti)Cx with an increased oxidation onset temperature (672 ± 2°C for Zr0.8Ti0.2C0.8).

Fabrication and electrical sliding wear of graphitic Cu–Cr–Zr matrix composites

Abstract The present work was undertaken to prepare graphitic Cu–Cr –Zr matrix composites in order to develop new materials for application under sliding contact in an electrical field. The electrical sliding wear behavior of the graphite (Gr)/CuCrZr composite was investigated from a microstructural viewpoint, compared with the matrix alloy. The results indicate that by using the water atomized Cu–Cr–Zr powder and copper-coated graphite particles as starting materials, compact and homogeneous microstructure can be obtained in the composites. Fine and coherent particulate precipitations are formed in the Cu–Cr–Zr matrix during the aging treatment process, which help to improve the mechanical properties. Under the electrical sliding wear condition, incorporation of graphite in the Cu–Cr–Zr matrix not only decrease the wear loss of the sliding pair but also maintain steady-state friction coefficient. The main reason is that the graphite film that smears on the contacting surfaces can alleviate materials loss induced by electric arc discharge and adhesion wear. Proper aging treatment helps to make full use of the solid lubricant effect of the graphite particles.

High strength Al–Li alloy development for laser powder bed fusion

With laser powder bed fusion (LPBF) of aluminum alloys growing in recent years, the research focus is progressively shifting from processing attempts on mature cast and wrought aluminum alloys to developing new aluminum alloy systems. This paper reports a novel Al–Li alloy specifically developed for the LPBF technology. The methodology of laser glazing on cast parts was applied to approximate solidification conditions of LPBF. Five variants of Al–Cu–Li ingots with different Sc and Zr contents were developed, and the optimized chemical composition was obtained and converted to Al–Cu–Li–Sc–Zr powder. This newly developed Al–Cu–Li–Sc–Zr alloy was successfully processed by LPBF with a high building rate and a low Li loss rate. The novel alloy shows excellent tensile properties including yield strength of 482 ± 1 MPa, ultimate tensile strength of 539 ± 1 MPa, and elongation of 8.8 ± 0.7%.

Reaction Mechanism of ZrB2-ZrC Formation in Ni-Zr-B4C System Analyzed by Differential Scanning Calorimetry.

The reaction mechanism of ZrB2-ZrC formation in a 30% Ni-Zr-B4C system under argon was revealed by using differential scanning calorimetry (DSC), X-ray diffraction (XRD) and scanning electron microscopy (SEM). The results indicated that the reaction mechanism in the Ni-Zr-B4C system was complex. Initially, NixZry and NixBy intermetallics were formed via solid-state diffusion reactions between Ni, B4C and Zr. Then, the eutectic reaction between Ni2B and Ni4B3 lead to the formation of Ni-B liquid. The free C atoms dissolved into the Ni-B liquid to form a Ni-B-C ternary liquid, and then part of the Zr powder dissolved into the surrounding Ni-B-C ternary liquid to form Ni-Zr-B-C quaternary liquid. Finally, ZrB2 and ZrC formed and precipitated out of the saturated liquid. The eutectic liquid plays an important role during the formation of ZrB2-ZrC.

Correction to: Stimulation of Spark-Plasma Sintering of Mixtures of Oxide–Non-oxide Components by Adding a Solid Solution of TaB2–NbC and through a Nickel Melt in Mixtures of Metal Powders

The effects of mixtures of Ni–Ta and Ni–Zr powders combined with sintered solid solution TaB2 –NbC during spark-plasma sintering of compositions at a pressing loading of 60 MPa in the range 1200 – 1600°C on the phase composition, percent content of Ti, Ta, and Zr in the sialon; microstructure; grain sizes of crystalline phases; relative density; linear shrinkage; physical-mechanical properties; linear correlation of the elasticity modulus and fracture toughness of mullite–β–SiAlON–TiC and mullite–β–SiAlON–c-ZrO2 samples are shown. Synthesized powders of β-SiAlON and TiC are characterized by extensive crystallization of β-SiAlON and TiC. c-ZrO2 spark-plasma sintered at 1400°C and solid solution TaB2 –NbC, at 1800°C, show extensive crystallization of c-ZrO2 and (Nb,Ta)C, B phases. The microstructure of solid solution TaB2 –NbC is crystalline, partially nonuniform, and almost completely sintered. Sintered samples with Ta and Zr additives show extensive mullitization; active crystallization of β-SiAlON, (Nb,Ta)C, B, and Ni(Nb,Ta); and varying crystallization of NiTi, NiTa, NiZr, and NiZr2 phases in the range 1200 – 1600°C. The microstructures of ceramic phases of samples with Ta additive are more uniformly and densely sintered. Particles of NiTi and NiTa in samples with Ta additive are uniformly and densely packed, unlike particles of NiTi, NiZr and NiZr, NiZr2 in samples with Zr additive. Sintering of compositions with Ta additive proceeds uniformly and extensively with formation of polydisperse compositions of crystalline phase grains. Samples with Ta additive show active growth and larger values of physical-mechanical properties, higher crack resistance, and better linear correlation of elasticity modulus and fracture toughness in the range 1200 – 1600°C.

An investigation of the tensile deformation mechanism of a high-oxygen Ti2448 alloy fabricated by powder metallurgy by use of the in-situ EBSD method

Ti2448 alloy fabricated by powder metallurgy using elemental powders of Ti, Nb, Zr and Sn exhibits good ductility but a high content of oxygen, and very limited work hardening in the tensile test. Its deformation mechanism is investigated by in-situ EBSD test conducted in an SEM equipped with a dynamic tensile stage. The results indicate that both dislocation slide and stress-induced phase transformation contribute to the plastic deformation of the alloy. Subsequent to yielding (after 3% of strain), β phase grains with preferential orientation 113β//X-axis tend to be transformed into α" martensite phase, which significantly reduces the plastic deformation caused by the dislocation slide and therefore leads to low work hardening.

Spatiotemporal and emission characteristics of laser-induced plasmas from aluminum-zirconium composite powders

Laser-induced plasmas and reactions therein depend on the ablated target's chemical composition and morphology. Recently, we have characterized plasma properties such as spatiotemporal morphology, electron density, species temperature within the plasma, ionization degree, etc. for pure Al under variations in morphology. Here, we utilize a bi-metal powder system to study similar characteristics as a function of powder chemistry. Micron-sized ball milled Al/Zr composites of three chemistries (3Al:2Zr, Al:Zr, and Al:3Zr) are compared to similarly-sized pure Al, pure Zr, and a mixture of Al + Zr powder. We find that the introduction of increasing concentrations of Zr has several interesting effects on the plasma compared to pure Al, including a dramatic increase in the electron density (to ~3–5 × 1020 cm−3), and the earlier onset of ZrO emission bands which have a higher disassociation energy and are thermodynamically preferred over AlO at high temperatures. Differences in plume morphology, the spatial distribution of molecular species, and the emission intensities of ZrO, Zr I and Al I were observed for Al + Zr and ball-milled Al:Zr samples, indicating the influence of microstructure on the chemical reactions. We measured plasma temperatures using the Saha-Boltzmann plot method; the composites demonstrate higher temperatures than pure Zr, Al + Zr mixtures, and pure Al. We observe only minor differences in temperature as a function of increasing Zr-content within the composites. This work continues to build on our understanding of the relationships between plasma properties and microsecond-timescale chemical reactions of reactive materials.

Laminated Ti3SiC2/Zr based composites obtained by spark plasma sintering

This paper is devoted to the fabrication of laminated Ti3SiC2/Zr based composites from Ti3SiC2 filled preceramic paper and Zr powder. The composites represented a “layers-by-layer” structure and were sintered by spark plasma at 1400 °C and 50 MPa for 10-30 min. The densification behavior during the sintering, microstructure of obtained composites and influence of the holding time on the phase composition were studied.

Effect of Zr addition on the interfacial reaction of the SiC joint brazed by Inconel 625 powder filler

Ni-based alloys are believed to be the most suitable brazing fillers for SiC ceramic application in a nuclear environment. However, graphite, which severely deteriorates the mechanical property of the joint, is inevitable when Ni reacts with SiC. In this paper, Different amounts of Zr powders are mixed with Inconel 625 powders to braze SiC at 1400 °C. When Zr addition reaches 40 wt%, the brazed seam confirms the absence of graphite. This research proves that Zr can avoid the graphite’s formation by suppressing Ni’s activity. The room-temperature shear strength of the joint with graphite’s absence is tested to be 81.97 MPa, which is almost three times higher than that of the joint with graphite. The interfacial reaction process and mechanism of the SiC joint are investigated and explained in this paper using thermodynamic calculations.

Combustion characteristics of zirconium particles coated with ferrite nanoparticles

To improve the properties of Zr powder for specific applications in aerospace and military fields, Zr powders were coated with ferrite nanoparticles, namely FeOOH, Fe2O3, and Fe3O4. An instantaneous flame propagation system and scanning electron microscopy, X-ray diffraction, thermogravimetry, and differential scanning calorimetry techniques was used to characterized the flame propagation characteristics, micromorphology, phase composition, crystal structure, thermal stability, and reactivity of the three types of nano ferrite-coated Zr particles. The results showed that, the flame propagation velocity and maximal temperature exhibited the following order: Fe2O3-coated > FeOOH-coated > Fe3O4-coated Zr dust cloud. With an increase in the proportion of coating materials, the combustion characteristics all decreased. The contrastive analysis of surface, ingredient and heating process revealed that, during combustion, in addition to inducing oxidation–reduction, inner Zr led to a replacement reaction with the outside ferrite coating layer, and then, Fe generated was oxidized at a high temperature.

Property of the Spheroidized Zr Powder by Radio Frequency Plasma Treatment

Property of the Spheroidized Zr Powder by Radio Frequency Plasma Treatment

Pre-Stabilization of Zr Getters for 5-Nine Purity Nitrogen Gas Purification

We confirm whether Zr powders can restrain a rapid nitrification reaction and offer a stable oxidation reaction according to temperatures in nitrogen gas purification. A pellet-type, porous Zr getter is prepared (diameter: 10 and thickness: 3 mm) using Zr powder with an average particle size of 45 μm. While maintaining the whole system, the Zr getter reaction is confirmed with an increase in temperature from 150 to 550 oC at increments of 100 oC under 99.999 % purity nitrogen atmosphere comprising of 10 ppm of impurity. Surface color, pore size, stabilized layer, and phase change are confirmed with optical microscopy, SEM-EDS, Micro-Raman, and X-ray diffraction (XRD) according to the Zr getter temperature. The surface color of the Zr getter changes from metallic silver to dark gray as temperature increases. In the EDS results, the nitrogen component is not observed, and oxygen content increases from each surface at elevated temperatures. The Raman and XRD results show the oxidation layer as a result of 350 oC annealing. Therefore, the Zr getter can be applied as a nitrogen getter under 5-nine purity nitrogen atmosphere after appropriate oxidized pre-stabilization process to prevent rapid nitrification reaction.

WITHDRAWN: Effect of Zr (rare earth) powder in the microstructure, tensile and compressive properties on Mg-6Zn alloy

Abstract Mg-6Zn alloy was used in various industries especially in the development of structural elements in automotive sector. Also this alloy was used in the development of bio-degradable human bio implants. In this research we have found the effect of alloying rare earth material (Zr) to the Mg6Zn alloy. The alloy was prepared through stir casting method. The mechanical properties such as tensile and compressive strength found to be increased with the addition of Zr. The structural studies were performed with the XRD and SEM. The composition of the added elements were analyzed with Energy Dispersive Spectroscopy (EDS). The phases formed was evaluated with the combination of EDS and XRD. The increase of Zr to the reduces the tensile strength upto 2% weight addition and decreases thereafter due to the lower bonding strength. On the other hand the compression strength increases with the addition of Zr.

Surface Modification of Biodegradable Mg-4Zn Alloy Using PMEDM: An Experimental Investigation, Optimization and Corrosion Analysis

ObjectivesMagnesium alloys are the potential candidate for metallic implants due to their excellent mechanical characteristics, biodegradable nature, and properties similar to human bone. However, a high degradation rate is primary obstacle in implementing these alloys as biodegradable orthopedic implants. Powder-mixed electric discharge machining (PMEDM) is an emerging method of surface modification of metallic alloys that can be implemented to improve the corrosion resistance of Mg alloys. Therefore, PMEDM using zirconium (Zr) and manganese (Mn) powder particles has been proposed to modify the surface characteristics of Mg-4Zn alloy. Materials and MethodsIn the present work, Zr and Mn powders have been used in varying concentrations during PMEDM of Mg-4Zn alloy. Experiments were conducted as per mixed design L18 orthogonal array (OA). Taguchi and Grey Relational Analysis (GRA) have been used to optimize the process parameters. Analysis of response characteristics, namely material removal rate (MRR), surface roughness (SR), and thickness of the alloyed layer (TAL), has been carried out at different values of input variables (like powder additives (Pa), powder concentration (Cp), peak current (Ip), pulse on time (Ton) and duty cycle (DC)). The corrosion analysis was carried out by immersing the specimen (machined at an optimized setting) in simulated body fluid (SBF). ResultsIt is observed from the analysis that Cp, Ip, and Ton play a pivotal role in evaluating response characteristics. The favorable setting suggested by the gray approach is Pa: Zr; Cp: 2 g/l; Ip: 4A; Ton: 50 μs; DC: 80%, while responses at this setting are confirmed by confirmation experiments with MRR: 32.14 mm3/min; SR: 5.578 μm and TAL: 8.28 μm. The immersion test signifies that the corrosion rate (CR) of PMEDMed sample (3.20 mm/year) is 40.74% lesser than the corrosion rate of polished sample (5.40 mm/year). ConclusionZr powder shows better performance in terms of higher MRR, lower SR and higher TAL as compared to Mn powder during the PMEDM process. The corroded surface of polished sample exhibited larger size micro pits and cracks than the machined sample, which concluded that surface modification of MZ-4Zn alloy via PMEDM is a powerful tool to enhance its corrosion resistance.

Synthesis and Thermal Stability of the Multielement Carbide (TaZrHfNbTi)С5

The multielement carbide (TaZrHfNbTi)С5 has been synthesized via two-step high-energy mechanical processing (HEMP). We have optimized mechanical processing parameters for the formation of the TaZrHfNbTi high-entropy alloy (HEA)—as a precursor for the synthesis of the mixed carbide—from a metal powder mixture. HEMP of a mixture of Ta, Zr, Hf, Nb, and Ti powders in an AGO-2 planetary mill for 15 min at 90g leads to the formation of a TaZrHfNbTi HEA with an imperfect crystal structure. The time needed for obtaining the multielement carbide (TaZrHfNbTi)С5 by milling a mixture of the metallic HEA and carbon black is 30 min. The thermal stability of the resultant carbide has been studied by high-temperature X-ray diffraction. The results demonstrate that the multielement carbide (TaZrHfNbTi)С5 is stable in the range 800–1200°C at an isothermal holding time of 5 h, without precipitation of individual carbide phases. Exposure to temperatures above 1000°C under dynamic vacuum leads to partial oxidation of (TaZrHfNbTi)С5.