ZrC Alloys Research Articles

Microstructural evolution and hardening of W-ZrC, W-1Re-ZrC and W-3Re-ZrC alloys induced by He ions irradiation

Bulk W-0.5 wt%ZrC (W-ZrC), W-1 wt%Re-0.5 wt%ZrC (W-1Re-ZrC), and W-3 wt%Re-0.5 wt%ZrC (W-3Re-ZrC) alloys were prepared and exposed to He2+ ion irradiation with an incident energy of 500 keV at 400 °C. Post-irradiation analysis revealed the formation of He bubbles, with consistent number density and average size across all alloys. However, the W-3Re-ZrC alloy exhibited a notably higher density of dislocation loops within grain interiors compared to W-ZrC and W-1Re-ZrC. This led to a significant increase in the hardening rate of W-3Re-ZrC to 61.5 %, nearly twice that of the other alloys. By considering the binding energies of He-vacancy, He-He, and Re-He, the formation and growth behavior of irradiation-induced defects, including He bubbles and dislocation loops, were also discussed. This work provides valuable insight into the relationships among Re alloying, He-induced defects, and irradiation hardening in Re-alloyed W materials, thus offering valuable guidance for the design of W-based plasma-facing materials.

Mechanical and corrosion properties of nano ZrC reinforced FeCrAl alloys

Purpose The purpose of this study is to investigate the effect of nano ZrC particles on the mechanical and electrochemical corrosion properties of FeCrAl alloys, providing a beneficial reference basis for the development of high-performance carbide reinforced FeCrAl alloys with good mechanical and corrosion properties in the future. Design/methodology/approach Nano ZrC reinforced FeCrAl alloys were prepared by mechanical alloying and spark plasma sintering. Phases composition, tensile fractography, corrosion morphology and chemical composition of nano ZrC reinforced FeCrAl alloys were analyzed by X-ray diffraction, scanning electron microscopy and energy dispersive X-ray spectroscopy, respectively. Microhardness and tensile properties of nano ZrC reinforced FeCrAl alloys were investigated by mechanical testing machine and Vickers hardness tester. Electrochemical corrosion properties of nano ZrC reinforced FeCrAl alloys were investigated by electrochemical workstation in 3.5 wt.% NaCl solution. Findings The results showed that addition of nano ZrC can effectively improve the mechanical and corrosion properties. However, excessive nano ZrC could decrease the mechanical properties and reduce the corrosion resistance. In all the FeCrAl alloys, FeCrAl–0.6 wt.% ZrC alloy exhibits the optimum mechanical properties with an ultimate tensile strength, elongation and hardness of 990.7 MPa, 24.1% and 335.8 HV1, respectively, and FeCrAl–0.2 wt.% ZrC alloy has a lower corrosion potential (−0.179 V) and corrosion current density (2.099 µA/cm2) and larger pitting potential (0.497 V) than other FeCrAl–ZrC alloys, showing a better corrosion resistance. Originality/value Adding proper nano ZrC particles can effectively improve the mechanical and corrosion properties, while the excessive nano ZrC is harmful to the mechanical and corrosion properties of FeCrAl alloys, which provides an instruction to develop high-performance FeCrAl cladding materials.

Evolution of Dislocation Loops in 30 keV He+-Irradiated W–0.5% ZrC Alloys: In Situ TEM Observations and Molecular Dynamics Simulations

Evolution of Dislocation Loops in 30 keV He⁺-Irradiated W–0.5% ZrC Alloys: In Situ TEM Observations and Molecular Dynamics Simulations

Effects of Fe-Ions Irradiation on the Microstructure and Mechanical Properties of FeCrAl-1.5wt.% ZrC Alloys.

Fe-13Cr-3.5Al-2.0Mo-1.5wt.% ZrC alloy was irradiated by 400 keV Fe+ at 400 °C at different doses ranging from 6.35 × 1014 to 1.27 × 1016 ions/cm2 with a corresponding damage of 1.0–20.0 dpa, respectively, to investigate the effects of different radiation doses on the hardness and microstructure of the reinforced FeCrAl alloys in detail by nanoindentation, transmission electron microscopy (TEM), and atom probe tomography (APT). The results show that the hardness at 1.0 dpa increases from 5.68 to 6.81 GPa, which is 19.9% higher than a non-irradiated specimen. With an increase in dose from 1.0 to 20.0 dpa, the hardness increases from 6.81 to 8.01 GPa, which is an increase of only 17.6%, indicating that the hardness has reached saturation. TEM and APT results show that high-density nano-precipitates and low-density dislocation loops forme in the 1.0 dpa region, compared to the non-irradiated region. Compared with 1.0 dpa region, the density and size of nano-precipitates in the 20.0 dpa region have no significant change, while the density of dislocation loops increases. Irradiation results in a decrease of molybdenum and carbon in the strengthening precipitates (Zr, Mo) (C, N), and the proportionate decrease of molybdenum and carbon is more obvious with the increase in damage.

Effects of rolling reduction on microstructural evolution and mechanical properties of W-0.5wt%ZrC alloys

The effects of hot rolling reduction on microstructures and mechanical properties of W-0.5 wt%ZrC (WZC) materials were investigated. Four WZC specimens with rolling reductions of 46%, 69%, 77%, and 96% were prepared by multi-step rolling processes. Metallographic observation, SEM, EBSD, and TEM characterization were conducted to obtain information on the microstructures of the materials. The metallography and EBSD results indicate that W grains were refined to 0.4–0.5 μm in the 96%-rolled WZC01 specimen. In addition, Vickers microhardness measurements at room temperature (RT) and tensile tests at various temperatures from RT to 500 °C were conducted. The results indicate that hardness and strength increase with the increase in rolling reduction. The 96%-rolled 1-mm thick WZC plate exhibits an ultra-high tensile strength of 1450 MPa at 100 °C. The 77%-rolled 6-mm thick WZC bulk material demonstrates both high tensile strength with an ultimate tensile strength of 620 MPa and good ductility with a tensile elongation of 21% at 400 °C, which are superior to those of most reported bulk W materials. The relationships between microstructure, mechanical properties, and rolling reduction were investigated and discussed systematically.

Fabrication of ultrafine grained FeCrAl-0.6 wt.% ZrC alloys with enhanced mechanical properties by spark plasma sintering

Low mechanical strength, especially at high temperatures, is the key problem that limit the application of FeCrAl alloys as the accident tolerance fuel (ATF) cladding materials. Dispersion strengthening by carbide nanoparticles is an effective way to improve mechanical properties at high temperatures. In this work, an ultrafine grained FeCrAl-0.6 wt.% ZrC alloys with excellent mechanical properties were fabricated successfully by mechanical milling and spark plasma sintering. The effect of milling speed on powder characteristics, microstructure and mechanical properties of FeCrAl alloys were investigated. The particle size of the powders increase significantly after milling at 400 rpm, while it has a lower oxygen content. Increasing the milling speed decreased the resultant grain size and improved relative density. Transmission electron microscope (TEM) demonstrated the nano ZrC particles uniformly distributed in the matrix at higher milling speed, which effectively promotes grain refinement and dispersion strengthening. The results of mechanical properties show that the tensile strength, percentage elongation and hardness of FeCrAl-0.6 wt.% ZrC alloys at room temperature (RT) reached up to 1.05 GPa, 349.86 HV and 12.1%, respectively, after milling at 400 rpm. It is worth noting that the FeCrAl-0.6 wt.% ZrC alloy also exhibited a good high-temperature strength more than 110 MPa at 800 ℃, which is about 55.4% and 24.7% higher than previously reported FeCrAl-0.5 wt.% ZrC and FeCrAl-1.0 wt.% ZrC alloys, but the plasticity is reduced. The results demonstrated that the excellent mechanical properties were not only attributed to the dispersion strengthen by nanosized ZrC, a good interface bonding between Fe matrix and nanosized ZrC, but also the ultra-fine grained structure induced by the milling process.

Synthesis and characterization of nano TiC dispersed strengthening W alloys via freeze-drying

In order to synthesize carbide dispersion strengthened tungsten (CDS-W) with high performance, the W-(0, 0.2, 0.5, 1.0 wt%)TiC alloys were synthesized by novel freeze-drying and low temperature sintering. When adding the optimum amount of 0.5 wt%TiC, the W–TiC composite powders possess finest grain size (about 30 nm). Afterwards, a prominent balance between the high density (98.3%) and ultrafine grain (680 nm) was achieved in the sintered W-0.5 wt%TiC alloys. Furthermore, the TiC particles (<50 nm) keep their original size and are uniformly distributed within W matrix. The ultrafine size of W grain and TiC particles are mainly attributed to the uniform doping of powder precursors and their stable phase interface. As a result, the sintered W-0.5 wt%TiC alloys possess the highest hardness (625 ± 38 HV0.2) among all the sintered samples. Based on above analysis, the new technology of freeze-drying can be employed to prepare W–ZrC alloys or other alloys with ultrafine grains and second phase particles.

Mechanical Properties, Thermal Stability and Microstructures of W-Re-ZrC Alloys Fabricated by Spark Plasma Sintering

Tungsten materials, used as friction stir welding tools, undergo severe plastic deformation and even collapse at high operating temperatures. In order to improve the low-temperature toughness and high-temperature strength, W-10wt.%Re-0.5wt.%ZrC alloys were processed by high-energy ball milling and subsequent spark plasma sintering. Single solid-solution W-Re powders with typical body-centered cubic structures were achieved when the milling time increases to 50 h. The microhardness, tensile properties, thermal stability and microstructures of this sintered W-10wt.%Re-0.5wt.%ZrC alloys were investigated. Synergetic effects of the solute Re and nanosized dispersion particles induce improvements in low-temperature toughness and high-temperature strength. The alloy suffers ductile fracture at 300 °C, which is about 400 °C and 300 °C lower than that of the spark plasma sintered pure W and W-0.5wt.%ZrC, respectively. Besides, this W-10wt.%Re-0.5wt.%ZrC has a high ultimate tensile strength of 818 MPa and uniform elongation of ~ 8.1% at 300 °C. Moreover, the microstructures and hardness remain stable even after 1500 °C anneal. Based on a detailed microstructure analysis, the mechanisms for the enhanced strength, low-temperature ductility and high thermal stability are proposed and discussed. Grain boundary mobility is impeded by the kinetics constraint through dispersed particles pinning and solute Re atoms dragging, which leads to improved thermal stability. The formation of Zr-C-O particles is most probably attributed to ZrC particles capturing and interacting with impurity oxygen during sintering.

Microstructure and high-temperature mechanical properties of second-phase enhanced Mo-La2O3-ZrC alloys post-treated by cross rolling

Excellent high-temperature mechanical properties and high recrystallization temperature are crucial for molybdenum (Mo) alloys in practical applications. The microstructure and high-temperature mechanical properties of Mo-0.8%La2O3-2%ZrC alloys prepared by traditional powder metallurgy technology associated with cross rolling post treatment were investigated. Results showed that the Mo1950-rolled alloys had a fine grain size of about 1.65 μm due to hot cross rolling and high tensile strengths of 988 MPa and 189 MPa at room temperature and 1400 °C, respectively. SEM and TEM examinations indicated that although most of the large La2O3 and ZrC particles were distributed along the grain boundaries, some nano-sized particles were well dispersed in intragranular zones. Particularly, dislocations were found to intercepted by the second phase particles in tensile samples, which could effectively enhance both the tensile strength and recrystallization temperature. Dislocation, grain refining, and second phase particles were all found to play important roles in strengthening the alloys below the recrystallization temperature, while second phase particle strengthening was the only strengthening mechanisms above the recrystallization temperature.

Synergistic effects of trace ZrC/Zr on the mechanical properties and microstructure of tungsten as plasma facing materials

Pure W, and W–0.5wt%ZrC (WZC) and W–2.0wt%Zr–0.5wt%ZrC (WZZC) alloys are fabricated using vacuum hot pressure (VHP) method to investigate the effects of trace ZrC or Zr/ZrC on the mechanical properties and microstructure of tungsten. It was found that from W to WZC and to WZZC, the average grain size was refined from 6.2 µm of W to 5.8 μm of WZC and finally to 4.8 um for WZZC and relative density increase continually from 97.0% to 98.0% and to 98.5%. The tensile tests indicated that ZrC or ZrC/Zr significantly increases the strength and ductility/plasticity. The comparison of VHPed and spark plasma sintered (SPSed) specimen are made. The microstructure analysis indicate that the W–Zr–O and/or Zr–C–O particles resulting from the reaction of Zr or ZrC with free O pin grain boundaries (GBs) of tungsten and inhibits the migration of GBs, and then refining the grain size. The synergistic effects of the decrease of free O impurity and nano-sized ZrC dispersion strengthening strengthen GBs and improve the mechanical properties.

Effects of swaging and annealing on the microstructure and mechanical properties of ZrC dispersion-strengthened tungsten

Nano-sized ZrC dispersion strengthened tungsten alloy (W-0.5wt%ZrC) rods with enhanced mechanical properties and superior high-temperature stability were fabricated by high temperature rotary swaging. The effects of swaging and annealing on the microstructure and mechanical properties of W-0.5wt%ZrC alloys were investigated. The as-swaged W-0.5%ZrC rod showed noticeable ductility at 200 °C with a total elongation of 4.2% and a tensile strength of 724 MPa, and at 500 °C the strength remains as high as 547 MPa and the total elongation is 28%. The ductile-to-brittle transition temperature (DBTT) is about 200 °C. The recrystallization start temperature of swaged W-0.5wt%ZrC is about 1500 °C, which is about 300 °C higher than that of rolled pure W. The possible mechanisms for the enhanced mechanical properties and thermal stability were discussed.

High thermal shock resistance of the hot rolled and swaged bulk W–ZrC alloys

The thermal shock (single shot) resistance and mechanical properties of the W–0.5wt% ZrC (WZC) alloys manufactured by ordinary sintering followed by swaging or rolling process were investigated. No cracks or surface melting were detected on the surface of the rolled WZC alloy plates after thermal shock at a power density of 0.66 GW/m2 for 5 ms, while primary intergranular cracks appear on the surface of the swaged WZC samples after thermal shock at a power density of 0.44 GW/m2 for 5 ms. Three point bending tests indicate that the rolled WZC alloy has a flexural strength of ∼2.4 GPa and a total strain of 1.8% at room temperature, which are 100% and 260% higher than those of the swaged WZC, respectively. The fracture energy density of the rolled WZC alloy is 3.23 × 107 J/m3, about 10 times higher than that of the swaged WZC (2.9 × 106 J/m3). The high thermal shock resistance of the rolled WZC alloys can be ascribed to their extraordinary ductility and plasticity.

Microstructure and Mechanical Properties of Nano-Size Zirconium Carbide Dispersion Strengthened Tungsten Alloys Fabricated by Spark Plasma Sintering Method**supported by the Innovation Program of Chinese Academy of Sciences (No. KJCX2-YW-N35), the National Magnetic Confinement Fusion Science Program of China (No. 2011GB108004), National Natural Science Foundation of China (Nos. 51301164, 11075177, 11274305), and Anhui Provincial Natural Science Foundation of China (No. 1408085QE77)

W-(0.2, 0.5, 1.0)wt% ZrC alloys with a relative density above 97.5% were fabricated through the spark plasma sintering (SPS) method. The grain size of W-1.0wt% ZrC is about 2.7 μm, smaller than that of pure W and W-(0.2, 0.5)wt% ZrC. The results indicated that the W-ZrC alloys exhibit higher hardness at room temperature, higher tensile strength at high temperature, and a lower ductile to brittle transition temperature (DBTT) than pure W. The tensile strength and total elongation of W-0.5wt% ZrC alloy at 700 °C is 535 MPa and 24.8%, which are respectively 59% and 114% higher than those of pure W (337 MPa, 11.6%). The DBTT of W-(0.2, 0.5, 1.0)wt% ZrC materials is in the range of 500°C–600°C, which is about 100 °C lower than that of pure W. Based on microstructure analysis, the improved mechanical properties of the W-ZrC alloys were suggested to originate from the enhanced grain boundary cohesion by ZrC capturing the impurity oxygen in tungsten and nano-size ZrC dispersion strengthening.

Grain growth behavior and mechanical properties of zirconium micro-alloyed and nano-size zirconium carbide dispersion strengthened tungsten alloys

Dense fine-grained pure W, W–1.0wt.%Zr (WZ), W–1.0wt.%ZrC (WZC) and W–1.0wt.%Zr–1.0wt.%ZrC (WZZC) alloys were fabricated by spark plasma sintering. The grains in WZ and WZZC alloys are stable at annealing temperatures below 1400°C (1h), while the grains in pure W grow significantly above 1100°C annealing. The tensile tests indicate that WZ is ductile already at 400°C, which is about 200°C lower than that for pure W. WZC exhibits higher hardness at room temperature than pure W. The ultimate tensile strength of WZC at 600°C is 798MPa, about 2.6 times that of pure W. Based on microstructural analysis, the good thermal stability of tungsten grains in WZ and WZZC samples is suggested to be originated from the W–Zr–O and/or Zr–C–O particles which are dispersed on or near the grain boundaries of tungsten and inhibit their migration. The improved tensile properties of the WZ, WZC and WZZC alloys originate (i) from the enhanced GB cohesion by Zr micro-alloying and (ii) from dispersion strengthening by nano-sized ZrC particles.

High temperature mechanical behavior of Nb–Mo–ZrC alloys

The microstructure and mechanical behavior of several Nb–Mo–ZrC alloys were investigated from room to elevated temperatures. Alloys with different compositions were prepared by arc-melting and homogenized. The resulting microstructure was characterized by optical microscopy, X-ray diffraction and electron probe microanalysis. Compression tests were performed to determine the stress–strain curve and 0.2% flow stress of each alloy. The results indicated the compressive yield strengths of Nb–ZrC alloys were improved significantly with Mo addition from room to elevated temperature. The improvement of strength in the Nb–Mo–ZrC alloy is mainly attributed to solid solution strengthening of the matrix.

Effect of alloy composition on microstructure and high temperature properties of Nb–Zr–C ternary alloys

The effect of alloy composition on microstructure and mechanical properties of Nb–Zr–C ternary alloys were investigated. Alloys were prepared arc melting and homogenized. The microstructure of the alloys were characterized by optical microscopy, X-ray diffraction and electron probe microanalysis. Compression tests were conducted from room temperature to 1773 K to determine the stress–strain curves and 0.2% flow stress. Fracture toughness of the alloys was determined using a single-edge-notched specimen under a three-point bending test. The results indicate that the 0.2% flow stress of the Nb–ZrC alloys increases with increasing ZrC content from room to elevated temperature. However, the compressive ductility and fracture toughness decrease with increasing ZrC content. A proper alloy design to obtain balance of high temperature strength and room temperature ductility is also discussed.

Influence of interstitial impurity on hydrogen solubility in zirconium.

Hydrogen solubility in Zr-N and Zr-C alloys with various compositions has been measured at a temperature of 8731, 048 K at a pressure below 100 Pa. All the solubility data closely obeyed Sieverts' law. The presence of carbon and nitrogen in zirconium increased the hydrogen solubility at a fixed pressure and provided the negative effect on the enthalpy of solution. Partial thermodynamic functions of hydrogen in the Zr-N and Zr-C alloys were obtained by a dilute solution model and compared to those obtained previously for Zr-O alloys. Dependence of partial molar quantities of hydrogen on interstitial impurity content in zirconium was discussed in terms of dilatometric effect, configurational effect and other contributions.

A new method for coating microspheres with zirconium carbide and zirconium carbide-carbon graded coats

A new method for the chemical vapor deposition of ZrC and C-ZrC alloys has been developed. This process has been applied to the fabrication of coated particle nuclear fuels of the type used in the large High Temperature Gas-Cooled Reactor. A powder feeder is used to supply ZrCl 4 to the fluidized bed coating furnace where it undergoes reaction with a hydrocarbon to form ZrC. Quantitative metering of the ZrCl 4 makes it possible to control the deposition of the ZrC and the codeposition of the C-ZrC alloys on the fuel particles. Examples of both types of coats made using the described technique are discussed and illustrated.

Arc Melting and Homogenization of ZrC and ZrC+B Alloys

A description is given of the methods used to arc-melt and to homogenize near-stoichiometric ZrC and ZrC-boron alloys, giving attention to the oxygen contamination problem. The starting material for the carbide preparation was ZrC powder with an average particle size of 4.6 micron. Pellets weighing approximately 3 g each were prepared at room temperature from the powder by the use of an isostatic press operated at 50,000 psi. These pellets were individually melted in an arc furnace containing a static atmosphere of purified argon. A graphite resistance furnace was used for the homogenization process.

Phase stability and mechanical properties of carbide and boride strengthened chromium-base alloys

Phase stability and mechanical properties of five carbide and two boride strengthened chromium-base alloys are presented. Compositions examined were Cr-0.5 TaC (mole pet), Cr-0.5 TiC, Cr-0.5 Cb(Nb)C, Cr-0.5 HfC, Cr-0.5 ZrC, Cr-0.5 CbB, and Cr-0.5 TaB. A transition in stability from the carbide of the principal alloying metal to Cr23C6, complete at approximately 2800°F, occurs in the Cr-0.5 TaC, Cr-0.5 TiC, and Cr-0.5 CbC alloys. Similarly, a change in phase stability from borides of columbium (niobium) and tantalum to Cr4B occurs at ∼2800°F in the Cr-0.5 CbB and Cr-0.5 TaB compositions. The compounds HfC and ZrC, respectively, remained stable in the Cr-0.5 HfC and Cr-0.5 ZrC alloys at this temperature. Stress-rupture properties at 2100°F improved for several alloys when aged at this temperature to precipitate the carbide or boride of the principal alloying metal following higher temperature heat treatment to form the Cr23C6 or Cr4B phases. Rupture life of the Cr-0.5 TaC alloy, for example, was increased at 15 ksi and 2100°F from 4 hr for as-fabricated material, to 186 hr after heat treatment. Improvement of rupture life for similar material and test conditions from 24 hr to 382 hr was observed in the Cr-0.5 TaB composition.