Zr Matrix Research Articles

A multi-level-variable correlated mechanistic model system for irradiation-induced multi-scale volume growths of U-10Mo/Zr dispersion nuclear fuels

Irradiation-induced volumetric deformations in dispersion nuclear fuels arouse a critical concern in nuclear fuel design. Utilizing the concepts from mesomechanics and homogenization, a multi-level-variable correlated mechanistic model system called the Dispersion Fuel Swelling Analysis Model System (DFSAMS) is developed for the irradiation-induced multi-scale volume growths of U-10Mo/Zr dispersion nuclear fuels. These models could directly correlate the macroscopic irradiation-induced volume growth strain with the dynamically varying multi-level information, including the obtained particle volume fractions, the current porosities of recrystallized zones of fuel grains, the macroscale porosities of fuel particles, the average numbers of fission gas atoms within fuel bubbles, the average bubble pressures and the macroscale pressures of fuel particles related to the macroscale hydrostatic pressures of dispersion fuels. The obtained theoretical results align favorably with finite element predictions and a diverse range of experimental data, demonstrating the effectiveness of the newly developed model system. It is indicated that: (1) the irradiation creep performance of the Zr matrix becomes the predominant factor influencing the macroscale volume growth deformations of U-10Mo/Zr dispersion fuels, due to the differed resistance to volumetric deformations of U-10Mo particles; (2) the as-fabricated bubbles of fuel particles will gradually decrease in size under the macroscale hydrostatic pressures due to the irradiation creep deformations occurring in the surrounding solid skeleton, contributing negatively to the macroscale volumetric expansion of U-10Mo/Zr dispersion fuels, especially in cases with higher initial porosity. The important theoretical models are supplied here for efficient numerical simulation of the irradiation-induced thermal-mechanical coupling behaviors in U-10Mo/Zr dispersion fuel elements.

Solidification-induced nonuniformity in U–Zr–RE metallic nuclear fuel rods

Metallic fuel is being developed for the next generation of sodium-cooled fast reactors due to its safety and fuel cycle economics through spent fuel reprocessing technology. After spent fuel reprocessing, rare earth elements that are immiscible with Uranium and Zirconium are included in the raw material for metallic fuel. Achieving a uniform composition and microstructure of RE inclusions is challenging because phase separation and temperature inhomogeneities during solidification lead to non-uniform composition and microstructure. This study explores the solidification and inclusion formation of U–Zr–RE metallic fuel rods. We show how RE inclusions are formed in the U–Zr matrix and how temperature inhomogeneities during solidification control the inclusion size distribution and edge migration of RE inclusions along the U–Zr–RE rods. Understanding the inhomogeneity of inclusions due to solidification can provide hints for making homogeneous nuclear fuel rods.

Expansion deformation mechanism and cracking behaviours of chromium-coated zirconium alloy cladding at room temperature

The deformation of the cladding tube triggered by the expansion of the internal plug is used to investigate the hoop deformation behaviour of the Cr-coated zirconium alloy cladding tube at room temperature. A thin-walled pressurized cylinder model is used to transform the axial load-displacement curve working on the expansion plug into the hoop stress-strain curve working on the cladding tube, and it is found that the Cr coating can be able to restrain the cladding tube from hoop deformation. Observation of the Cr-coated cladding tube after different amounts of hoop deformation revealed that the strain corresponding to the generation of the first crack was a ranged from 0.48 % to 0.59 %, the density of cracks started to grow very fast and then entered a saturation stage. The fracture strength of the Cr coating and maximum interfacial shear strength when the Cr coating crack density reaches saturation were calculated by the shear-lag model. Twins and a large number of dislocations were generated in the Zr matrix and a small number of dislocations in the Cr coating after the hoop deformation. The behaviour of crack initiation and propagation occurring in Cr coating is revealed.

Revisiting the thermodynamic properties of the ZrCr2 Laves phases by combined approach using experimental and simulation methods

A comprehensive study of ZrCr2 Laves phases is important for both fundamental research and technological applications. The ZrCr2 compound is a typical precipitate observed in Zr-based alloys including the newly developed Cr-coated Zr cladding known as Accident Tolerant Fuel cladding. The brittle behavior of the Laves phases and the low melting point at the interface zone between the precipitates and the Zr matrix are considered as governing the thermomechanical behaviors of these newly developed nuclear fuel claddings for normal operating conditions but more dramatically in case of Loss Of Coolant Accident (LOCA) conditions. The aim of the present study is to investigate the various ZrCr2 Laves polymorphs and their thermodynamic features particularly where conflicts exist in the literature. Based on diffraction experiments of annealed samples, it has been established that the transformation from the C14 high-temperature form to the C15 low-temperature form is of displacive nature without the C36 polymorph forming as an intermediate phase. The stable and metastable domains of C14 and C15 and their thermodynamic properties have been determined. The specific heat of both C14 and C15 types was measured over a wide range of temperatures from 2 to 1063 K by coupling relaxation calorimetry and DSC. The experimental data were fitted using a modified Einstein model. The room temperature entropies of the C14 and C15 phases were evaluated. The enthalpy of formation was measured for the first time using drop solution calorimetry in liquid Al at 1173 K in a Tian–Calvet calorimeter. The experimental value is in good agreement with Density Functional Theory (DFT) calculations. Finally, all these new results are discussed regarding the abundant literature on the ZrCr2 Laves phases.

Post-quench ductility limits of coated ATF with various zirconium-based alloys and coating designs

Post Quench Ductility (PQD) of various Cr-coated cladding designs with respect to base cladding materials, Cr coating methods, and its thickness were investigated to explore Emergency Core Cooling System (ECCS) limits. Both inner wall and outer wall of coated (Cr and Cr/CrN) claddings were steam oxidized at ∼1204 °C and then water quenched. The post-oxidized specimens were ring compressed to attain offset strains based on which ductility was assessed in compliance with the U.S. Nuclear Regulatory Commission (U.S. NRC)’s protocols. Weight gain-based Equivalent Cladding Reacted (ECR) limits of coated specimens (Cr and Cr/CrN) are consistently lower than those of the base cladding materials due to the early load drop under Ring Compression Test (RCT). Yet, time needed to reach the ECR limit is still increased for coated specimens because it effectively undergoes single side oxidation with protective coating. Cracks imitated from ZrCr2 are primarily responsible for the early major load drop observed for tested coating thicknesses (8.9 µm and 18.9 µm), and hence reduced ECR limits compared to bare Zircaloy. The cracks from ZrCr2 was promoted by an increased oxygen concentration of the interfacing Zr matrix owing to the diffusion of oxygen through the coating. The thicker coating reduces this oxygen level, thereby delaying the load drop from ZrCr2 during RCT and increases the ECR limit. The maximum attainable ECR limit of coated ECR limits is affected by the base Zircaloy as it gives as the ECR ceiling from which ECR reduction for coated cladding occurs. For the tested base cladding materials (Opt. ZIRLO™ and HANA-6), ECR 19 %, which is the limit for Cr-coated (8.9 µm) HANA-6, may serve as the lower envelope limit. Hence, ECR 19 % (single-side ECR) can conservatively serve as the conservative, yet non-design specific, Cr-coated ECR limit for the most of the modern base Zircaloy materials (Opt. ZIRLO™ and HANA-6).

Processing, mechanical, corrosion, and wear behavior of ZnO-reinforced Mg and Mg–Zr matrix composites for bioimplant applications

The need for efficient biodegradable material for implants has been rising due to issues related to the rate of degradation, toxicity, and osseointegration. This work aims to study the mechanical, corrosion, and wear behavior of ZnO nanoparticles reinforced Mg and Mg–Zr Matrix composites processed using powder metallurgy for bioimplant applications. The magnesium powder with ZnO nanoparticles and Zr microparticles was blended, compacted at 550 MPa, and subsequently sintered at 450 °C for 2 h. The synthesized composites were characterized in terms of structure, microstructure, densification, microhardness, wear, and in vitro corrosion analysis in simulated body fluid. The results showed that ZnO with Zr significantly altered the basal structure of Mg and underwent grain refinement with uniform distribution of ZnO predominantly near grain boundaries. Close to 99 % densification with 50 % enhancement in microhardness was obtained for the Mg–Zr–ZnO composite in comparison to pristine Mg. Moreover, the wear characteristics of the Mg–Zr–ZnO hybrid composite showed enhancement in wear resistance by 35 % relative to pure Mg. Corrosion assessment of the processed Mg composite samples was systematically performed in simulated body fluid (SBF). The obtained results confirmed the enhanced corrosion-resistant performance of Mg–Zr–ZnO samples in SBF medium. The refined microstructure and synergistic impact of Zr and ZnO particles as reinforcement in hybrid Mg composite have improved microhardness, corrosion, and wear characteristics, making it a potential bioimplant material.

Heterogeneous deformation-induced strengthening of extruded Tip/WE43 composites

Titanium (Ti) particles reinforced WE43 (Mg-4Y-2Nd-1Gd-0.5Zr) matrix composites (Tip/WE43) were prepared via ultrasonic-assisted stirring casting and following hot extrusion. Ti particles can refine the grains and promote the precipitation of the second phases in magnesium (Mg) matrix. Meanwhile, bimodal structures combining coarse deformed grains and recrystallization equiaxed grains were formed. The generation of heterogeneous interfaces promotes heterogeneous deformation-induced (HDI) strengthening. Extruded 3Tip/WE43 with a yield strength (YS) of 241 MPa, an ultimate tensile strength (UTS) of 283 MPa, and an elongation (EL) of 17.3%, respectively, possesses an excellent strength–ductility combination. The interfacial product of Ti/Mg was mainly composed Ti3Al layer with about 200 nm, which was conducive to interfacial bonding and stress transfer. The dislocation entanglements and stacking faults inside the Ti particles can promote the coordinated deformation between the Mg matrix and Ti particles. The rare-earth rich phases Ti2ZrAl, Mg41Nd5, and Mg24Y5 precipitated in the matrix can hinder dislocation movement by activating Orowan strengthening. The key factors of YS increment of the composites were considered to be HDI strengthening, fine grain strengthening, and thermal mismatch strengthening.

A new design of composite fuel with Zr-coated TRISO particles dispersed in metal matrix

With the development of advanced reactors, it is critical to improve the safety of nuclear reactors. Safety primarily depends on the ability to block fission products and the ability to discharge decay heat of fuel elements. To enhance the ability to retain the release of fission products and achieve high thermal conductivity, a novel fuel pellet was developed, consisting of zirconium (Zr)-coated TRISO particles embedded in a zirconium metal matrix. The zirconium coating was deposited via fluidized-bed chemical vapor deposition (FB-CVD), and the deposition mechanism of Zr coating via FB-CVD was proposed. The consolidation process of Zr-coated TRISO particles in the Zr matrix was achieved via spark plasma sintering (SPS). The microstructure and mechanical properties of Zr coating and the pellet were investigated via SEM and nanoindenter. The results proved the effectiveness of zirconium coating in preventing TRISO fuel particles from contact and cracking during sintering.

Morphology prediction of elastically interacting Zr hydride precipitates and cracks in [formula omitted]-Zr using atomistically informed Eshelby’s ellipsoidal inclusion

We propose an atomistically informed Eshelby’s inclusion analysis to investigate the morphology of secondary phases, which elastically interacted with each other through their respective local strain fields. Using the proposed method, we predict the morphology of δ-hydride precipitates and cracks, which interacted in the α–Zr matrix. Planar cracks nucleate along the basal-normal δ-hydride disk. And at the crack tip, the prismatic-normal δ-hydride disk also nucleates depending on the stress condition around the crack, constructing the hydride-crack network. The findings contribute to the understanding of the fracture mechanism of Zr alloys, such as delayed hydride cracking, which is caused by Zr hydride.

Microstructure and mechanical properties of hydride blisters formed on Zircaloy-4 claddings

To assess the microstructural and mechanical characteristics of hydride blisters formed on Zircaloy-4 tubes, we employ the electron backscatter diffraction (EBSD) analyses and micro-cantilever failure tests directly on the hydride blister (HB) area. In the HB area, more than 70% of the blister area is characterized to be δ-hydride, and the HB area does not favor the orientation relation ((101¯1)α//(001)δ, [12¯10]α//[1¯10]δ) that is otherwise well-matched in the Zr matrix area. The geometrically necessary dislocation density is observed in the entire blister area, indicating a large amount of strain throughout the blister area. Also, the deformation strain is concentrated in both the hydride and α-Zr phases of HB areas; however, the hydride underwent intensive deformation in the Zr matrix. The average fracture toughness of the hydride blister area obtained through the micro-cantilever test is 1.81 MPam, indicating a brittle fracture that may threaten the integrity of spent nuclear fuel claddings.

Abrasive Wear and Physical Properties of In-Situ Nano-TiCx Reinforced Cu–Cr–Zr Composites

Cu–Cr–Zr alloys reinforced in situ with TiCx nanoparticles were prepared via combustion synthesis and electromagnetic stirring casting. The microstructure of TiCx/Cu-Cr-Zr composites with various contents was analyzed. The microhardness and Brinell hardness of the composites were determined; the average volumetric abrasive wear rate and worn surface of the composites were investigated; and the electrical, thermal conductivity and thermal expansion coefficients of the materials were discussed. The results indicated that the addition of TiCx particles transformed the Cu–Cr–Zr matrix alloy microstructure from a dendritic to an equiaxed crystal, and the grain size was significantly refined as the amount added was increased. The composites with high TiCx content possessed higher hardness and abrasive wear resistance. The addition of TiCx particles reduced the electrical and thermal conductivity and thermal expansion coefficients of the materials.

Novel carbon nanotubes reinforced Ti28Nb35.4Zr matrix composites fabricated via direct metal deposition for bone implant applications

In this study, new β Ti-28Nb-35.4Zr (hereafter denoted TNZ) and multi-walled carbon nanotubes (MWCNTs; 0.1 wt.%) reinforced TNZ composite (hereafter denoted TNZCNT) were manufactured for bone implant applications via direct metal deposition (DMD). The effect of MWCNTs addition was systematically investigated on the microstructure and resultant mechanical, nano-tribological, and biocompatibility properties of TNZ. Results indicated that the microstructures of TNZ and TNZCNT composite were primarily composed of β along with localized α″ martensite phases. TNZ and TNZCNT composite exhibited average compressive yield strengths of 706 MPa and 833 MPa, respectively, with outstanding plastic deformation ability (>55%) without forming cracks and fractured surfaces under high compressive loads. Average nanohardness of TNZ and TNZCNT composite was measured as 2.9 GPa and 3.4 GPa, respectively. Compared to average wear volume of TNZ counterpart (0.19 µm3), nano-tribological tests also revealed higher resistance of TNZCNT composite to wear (0.07 µm3) owing to its higher hardness. MTS assay revealed that both TNZ and TNZCNT composite exhibit high viabilities of SaOS2 cells measured as 97.6% and 107.6%, respectively, after 7 d of cell culturing. Moreover, TNZCNT composite exhibited thriving adhesion and spreading of SaOS2 cells showing their growth and proliferation on its surface after cell culture for 1 and 7 d, demonstrating its extraordinary biocompatibility. Overall, owing to their appropriate mechanical, nano-tribological, and biocompatibility properties, the DMD-manufactured TNZ and TNZCNT composite displayed promising potential to be utilized as a candidate material for load-bearing implant applications.

Simulating the carbon distribution in zirconium alloy spent fuel cladding

The diffusivity values of C in pure Zr and in Zr containing dissolved O (Zr(O)) were determined in a temperature range of 623–1023 K for Zr and 923–1123 K for Zr(O) from depth profiles of C obtained by glow-discharge emission spectroscopy. The C diffusivity in Zr(O) decreased as the O concentration in Zr increased and that for Zr containing 15 at % O was two orders of magnitude smaller than that for pure Zr. One-dimensional numerical calculations of Fick’s diffusion equation with a Soret effect indicated various non-uniform distributions of C in a 5-mm-thick Zr matrix under a temperature gradient of 573 to 773 K for 3 years, assuming a heat of transport of − 1.5 to + 1.5 eV. Isothermal annealing at 773 K for 10 years could result in a uniform distribution, whereas dissolution of O in the interstitials of the Zr matrix would hinder C transport through the interstitials.Graphical As concentration of O increased in HIP Zr by 15 at%, the diffusivity of C decreased more than two orders of magnitude.For the positive {{Q}^{*}}_{c}, concentration of C slightly segregated at the surface of the cooler side but had maximum peaks at a middle to a higher temperature zone, and depleted at the surface of the hotter side.For the negative {{Q}^{*}}_{c}, concentration of C depleted at the surface of the cooler side and at the middle to the higher temperature zone, and highly segregated at the surface of the hotter side.

Atomic‐Scale Investigations of H3BO3and LiOH on Zr(0 0 0 1) Surface: A DFT Study

AbstractThe boric acid (H3BO3) and lithium hydroxide (LiOH) are routinely added to primary water as soluble neutron absorbers and pH regulating agents in the pressured water reactor nuclear power plant, respectively. Previous studies mostly focus on the service behavior of nuclear materials using experimental methods, whereas the microscopic mechanism of H3BO3and LiOH on Zr‐based fuel cladding remains largely unclear. With the first principle approach of density functional theory (DFT), the geometric structure, Mulliken population, partial densities of states, and electron density difference are adopted to study the adsorption characteristics and binding strength of H3BO3and LiOH on Zr matrix. The results show that when H3BO3and LiOH react on the Zr matrix, there is formation of hybrid peaks and new bonds between surface molecules and the matrix. Meanwhile, the vertical molecule has a substantial impact on electron movement between adsorbs and the matrix. The interaction energy between two molecules and the Zr surface in turn is LiOH > H3BO3, demonstrating that LiOH has the most influence on the fuel cladding in the primary circuit.

Microstructures and Mechanical Properties of V-Modified Ti-Zr-Cu-Ni Filler Metals

TA2 titanium alloy was brazed with Ti-Zr-Cu-Ni-V filler metals developed in a laboratory. The melting properties, the microstructures, phase compositions of filler metals and wettability, erosion properties, tensile properties of the brazed joint were studied in detail. The results show that with the increase of V content, the solidus-liquidus temperature of Ti-Zr-Cu-Ni-V filler metals increased, but the temperature difference basically remained unchanged, trace V element had a limited influence on the melting temperature range of Ti-Zr-Cu-Ni filler metals. The microstructure of Ti-Zr-Cu-Ni-1.5V filler metal was composed of Ti, Zr matrix, (Zr, Cu) solid solution and crystal phase. With the addition of V content, these phases containing V such as Ni3VZr2, NiV3, Ni2V in the molten filler metals increased. V was more inclined to combine with Ni to slow down the diffusion of Ni to titanium matrix. The wettability of filler metal with trace (≤0.5 wt.%) V to TA2 titanium alloy became worse, the wettability improved significantly with continuous increase of V content. The thickness of embrittlement layer and intergranular infiltration region decreased significantly by adding V. With the increase of V content, V could regulate the brazing interface reaction, more strengthened phases generated, which resulted the significant increase of the strength (302.72 MPa) and plasticity index (16.3%) of the brazed joint with Ti-Zr-Cu-Ni-1.5V filler metal.

Theoretical study on adsorption and dissociation of Li3BO3 and LiBO2 molecules on Zr(0 0 0 1)

In this work, the geometric structure, the Mulliken population, the partial densities of states, and the electron density difference were used to study the adsorption characteristics and binding strength of Li3BO3 and LiBO2 on Zr matrix using the first principle approach of density functional theory (DFT). As a consequence, when the Li3BO3 and LiBO2 react on the Zr matrix, hybrid peaks form, and new bonds are formed between the surface molecules and the substrate. Meanwhile, the vertical molecule has a substantial impact on electron movement between adsorbs and the matrix. The interaction energy between two molecules and the Zr surface in turn is LiBO2 > Li3BO3, demonstrating that LiBO2 has the most influence on the Zr surface.

Using θ′ interfaces as templates for planar L12 precipitation in AlCuMnZr alloys

• Al 3 Zr L1 2 / θ' co-precipitates form faster in additively manufactured Al-Cu-Mn-Zr (ACMZ) alloys • Rapid solidification allows for higher matrix solute contents • Interfacial Zr segregation rate is dependent on the Zr matrix content • Theta prime precipitates are perfect templates for planar Al 3 Zr L1 2 formation Controlled Mn and Zr additions to Al-Cu alloys have allowed for the improved retention of mechanical properties after extended 350°C exposures by stabilizing the main strengthening θ' (Al 2 Cu) phase. Ultimately, θ' /L1 2 (Al 3 Zr) co-precipitate formation stabilizes θ' most effectively; however, Zr diffuses sluggishly and has low solubility in aluminum castings. Increasing the Zr segregation rate would allow for faster and more effective θ' /L1 2 co-precipitation. It is demonstrated that the Zr segregation rate is faster when the Zr matrix content is higher. A much higher Zr matrix content facilitated by rapid cooling during additive manufacturing (AM) was achieved that produces faster θ' /L1 2 co-precipitation, which is shown by scanning transmission electron microscopy and atom probe tomography experiments. It was also found that Zr continuously segregates to θ' interfaces up to the most aggressive heat treatment studied such that planar L1 2 precipitates remain after the metastable θ' dissolves. In this manner, we demonstrate that θ' coherent interfaces serve as perfect templates to form stable planar L1 2 precipitates that can provide strength at higher temperatures than traditional θ' strengthened AlCu alloys. This work introduces an alloy design strategy that uses metastable precipitates to quickly nucleate and grow co-precipitates with a desired geometry that contain slow diffusing elements. These ideas can be applied to engineer more heat resistant alloys by taking advantage of high solute matrix contents enabled by rapid cooling during additive manufacturing.

Study of Zr addition on the composition, crystallite size, microstructure and properties of high-performance nano Cu alloys prepared by mechanical alloying

Although nanostructured Cu alloys prepared show great advantages in performance, the excellent properties have not been achieved at present primarily due to a single strengthening method or the Fe contamination introduced during mechanical alloying. In the present work, an appropriate amount of Zr was added to adjust the milling process and Fe contamination in the Cu matrix. Then the effects of Zr on the morphologies, crystallite sizes, lattice strain, composition and properties were analyzed. When the added Zr content was 0.1 wt%, it could promote the work hardening of Cu powders, resulting in smaller crystallite sizes, larger internal strain. And a slightly higher Fe content was introduced. However, with the increase of the Zr content, the Fe contamination was reduced obviously and the crystallite size began to increase again. Even so, the average crystallite sizes of nanostructured Cu alloys were still less than 20 nm. The results also showed that MA could increase the solid solubility of Zr in Cu. In a word, the properties of the nanostructured Cu alloys were improved by the refinement strengthening of matrix, solid solution and dispersion strengthening of Fe and Zr. The optimum properties were achieved by Cu-0.1 wt% Zr with electrical conductivity of 75.19% IACS and tensile strength of 526 MPa. The study provided a new route for overcoming Fe contamination in the metal matrix, and further improving the properties of Cu alloys through various strengthening methods.

Purification and Characterization of High Purity Nano Zirconia by Liquid-Liquid Extraction Using D2EHPA/p-Xylenes

In this paper, Zr(IV) nitrate solution decomposed from Viet Nam zircon concentrate was the source of zirconium extraction by liquid-liquid extraction (L.L.E). The FT-IR and UV-Vis spectra confirmed the extraction of Zr(IV) by D2EHPA/p-xylenes. There were four stages for the purification of impurities from the Zr matrix. First, the extraction of elements in 3.0 M HNO3 by 50% D2EHPA/p-xylenes was conducted. Second, two scrubbing cycles of impurities using 6.0 M HNO3, 76.5% of the total amount of Zr(IV) were retained in the organic phase, and 23.5% remained in the aqueous phase. Third, the stripping of a macro amount of zirconium from loaded D2EHPA has been effectively carried out using 1.5 M H2SO4 with a stripping efficiency of 99.6%. Fourth, concentrated ammonia was added to the solution Zr(IV) after stripping extraction to form precipitate for calcination at 550 °C for the final products. The refined products were characterized by X-ray diffraction, scanning electron microscopy (SEM), transmission electron microscopy (TEM), EDS, XRF, and diffuse reflectance spectroscopy. The ZrO2 has high purity, is nanospherical, and has a uniform sphere-like morphology with small grain size of less than 30 nm and a bandgap value of about 3.30 eV.

Microstructure and enhanced mechanical properties of ZrC/Zr composites added by in-situ Y2O3 reinforced particles

The in-situ hybrid particle-reinforcements are a novel strengthening mode for the advanced metal matrix composites. In this study, Zr matrix composites incorporating the fixed amount of ZrC particles with the different amounts of Y2O3 particles were prepared by the in-situ reaction among Zr, graphite, Y, and ZrO2 during the arc-melting. Results revealed that the graphite/Zr reaction produced the uniform in-situ ZrC particles in the Zr matrix, and the Y/ZrO2 reaction formed the Y2O3 particles. In-situ Y2O3 addition refined the Zr matrix and led to the polygonal morphology of the ZrC particle. The coarser Y2O3 grew in bulk, and some fine Y2O3 dendrites were formed along Zr boundaries. The influence of different contents of Y2O3 reinforcements on the hardness and compressive properties were analyzed. Compared with the single ZrC reinforcements, the hybrid Y2O3 introduction resulted in a higher hardness and enhanced compressive strength. This hybrid structures were believed to be favorable to mechanical responses in the composites, and the relevant mechanisms for the hardening and strengthening effect of such hybrid forms were discussed.