ZrB2 Particles Research Articles

Optimal Tungsten Inert Gas Welding Parameters of Dissimilar Aluminum Alloys Al 7075 and Al 6061 Using Ultrasonic Vibration and Nanocomposite Filler (Al 5356/ZrB2) to Alleviate Hot Cracking Phenomenon

Abstract In this study, the welding of dissimilar aluminum alloys, Al 7075 and Al 6061, was investigated using Al 5356 filler rods reinforced with ZrB2 particles. The welding process was conducted using tungsten inert gas (TIG) welding, with and without ultrasonic vibration, to enhance weld quality and reduce hot cracking. Optimization of process parameters for dissimilar TIG welding was performed through Response Surface Methodology (RSM), which generated a design matrix to analyze the influence of process parameters on response variables. Numerical and graphical optimization was applied to minimize hot cracking sensitivity and maximize microhardness. The RSM-based models suggested an optimal welding current of 93 A, the use of Al 5356/ZrB2 nanocomposite filler, and the application of ultrasonic vibrations. Experimental validation of the identified solution demonstrated improvements in weld quality, including increased yield strength and ductility. The combination of nano-reinforced fillers and ultrasonic vibrations was found to enhance weldability and mitigate hot cracking in dissimilar aluminum joints. The mechanism of hot cracking reduction involved grain refinement, degassing, and homogenization due to ultrasonic vibrations, as well as the modification of weld pool chemistry and control of dilution by the nanocomposite filler, which collectively minimized solidification shrinkage and stress. Under these optimized conditions, no hot cracking was observed experimentally.

Corrosion and wear performance and mechanism study of ZrB2/AA6016

Abstract This study involved the fabrication of aluminum matrix composites reinforced with ZrB2/AA6016 particles using the KBF4-Al-K2ZrF6 reaction system， the composites were then subjected to T6 heat treatment. An investigation was conducted to examine the impact of varying friction speeds on the corrosion and wear characteristics of ZrB2/AA6016. An investigation was conducted to study the frictional wear behavior of ZrB2/AA6016 in the presence of 3.5wt. % NaCl, both before and after T6 heat treatment. The study also aimed to understand the underlying mechanism of this behavior. The results indicate that the T6 heat treatment mitigates the impact of thermal stresses and strains caused by thermal mismatch, hence enhancing the material's wear resistance. The coefficient of friction (COF) for heat-treated ZrB2/AA6016 is lower than that for unheated-treated ZrB2/AA6016. As friction increases, the pace at which the material wears down tends to decrease. At a friction wear velocity of 50 mm/s, the wear rate of the material is minimized both before and after heat treatment, measuring 0.23×10-2mm3/Nm and 0.22×10-2mm3/Nm, respectively. Through the utilization of XRD, SEM, EBSD, TEM, and XPS analytical techniques, it has been determined that the ZrB2 particles exhibit strong bonding with the Al matrix. Additionally, the particle diameters range from 50~150nm. Following the T6 heat treatment, the grain size measured 40.53μm, while the proportion of large-angle grain boundaries was found to be 66.4%. The accumulation of Cl- resulted in the formation of localized corrosion pits on the surface undergoing wear, hence hastening the deterioration of the material. The primary causes of wear failure are corrosive wear, abrasive wear, and oxidative wear.

Effects of zirconium diboride addition on porosity reduction in laser metal deposition of tungsten carbide–cobalt cermet material

Laser metal deposition of tungsten carbide–cobalt (WC-Co) cermet material is a promising means of improving the wear resistance of metal products. However, laser metal deposition of WC-Co has constraints on its practical use because a clad bead of WC-Co often includes numerous gas pores. Earlier studies have found CO gas generation in a molten pool by reaction of carbon and oxygen to be the main cause of gas porosity in a WC-Co clad bead. Preventing the gas reaction is important to obtain clad beads with few pores. The addition of elements with strong affinity for oxygen, such as aluminum, was found to be effective for porosity reduction in a clad bead. However, the addition of highly reactive pure aluminum particles on WC-Co powder presents some difficulties for industrial use. For this study, zirconium diboride (ZrB2), a chemically stable compound, was used as an additive to WC-Co powder. After WC-Co powder with adhered ZrB2 particles was prepared using a wet granulation process, laser metal deposition was conducted. Zirconium stemming from the dissolution of ZrB2 in the molten pool was found to have the effect of trapping oxygen elements as solid zirconium oxides. Consequently, gas generation in the molten pool by the reaction of carbon and oxygen was restrained. Clad beads having few pores and fine microstructures were obtained. Observations of the molten pool behavior taken using a high-speed camera indicated that ZrB2 addition drastically improves process stability compared to processes using conventional WC-Co powder.

Insight into microstructure evolution of in-situ ZrB2np/AA6111 composites with both excellent room and high temperature properties

With rapid development of aerospace and automobile, the service condition of structural components becomes increasingly harsh, diverse and high mechanical properties are urgently needed. In this work, an advanced in-situ ZrB2np/AA6111 composite with excellent room and high-temperature properties was prepared via Al-Zr-B reaction system. The microstructure revealed that ZrB2 nanoparticles with regular polygonal shapes ranged from 10 to 150 nm approximately, and a good α-Al/ZrB2 interface bonding was confirmed. The agglomeration of ZrB2 particles was significantly weakened during hot extrusion. Due to the inhibiting effect on dislocation motion and pinning effect on grain boundaries induced by ZrB2 particles, fine recrystallized grains were obtained in ZrB2/AA6111 composites after extrusion. Compared with AA6111 matrix alloy, the yield strength, ultimate tensile strength and elongation of AA6111-3ZrB2 composites at room temperature and 300 °C were increased by 18.9 %, 12.7 %, 50.0 % and 34.1 %, 22.4 %, 42.4 %, respectively. An excellent room and high-temperature strengthening effect was simultaneously achieved assisted by ZrB2 particles. The improvement of room-temperature properties was mainly owed to the Grain refinement and Orowan bypassing strengthening mechanisms. The good high-temperature properties mainly relied on the superior coarsening resistance of ZrB2 particles which could fully played the Orowan strengthening effect and well protected the grain boundaries at high temperature. This work provides a feasible approach to design high-performance aluminum alloys and is beneficial for the further development of modern industries.

Effect of SiC dominated with ZrB2 particles on the ablation and mechanical properties of carbon/novolac‐epoxy (EPN1180) composite at 3000°C

AbstractThis study investigates the mechanical properties and erosion resistance of high temperature–pressure carbon‐epoxy novolac insulation reinforced with ZrB2/SiC particles. For this reason, at first, five samples were fabricated using the hot press, which included resin epoxy novolac EPN1180 base without reinforcement and four samples containing resin with 20:80, 30:70, 40:60, and 50:50 of SiC: ZrB2 particles respectively. After manufacturing of the samples, the mechanical properties were evaluated through bending and tensile testing, followed by erosion resistance properties by the use of oxyacetylene flame erosion tests. Chemical composition and surface morphology analysis of the composites were conducted using energy‐dispersive spectroscopy, scanning electron microscopy, and x‐ray diffraction analysis. Results indicate that the addition of ceramic particles enhances both mechanical properties and erosion resistance of the composite. The pure resin sample exhibited the highest weight loss and thickness reduction, while the sample containing 40% SiC and 60% ZrB2 demonstrated the least weight loss and thickness reduction about 55% and 83% respectively compared to pure sample. Additionally, the sample with 30% SiC and 70% ZrB2 had the lowest backside temperature. Furthermore, the sample with 20% SiC and 80% ZrB2 exhibited the highest mechanical properties, with a tensile strength of 422.5 MPa and flexural strength of 587.11 MPa. Morphological analysis revealed the presence of phases such as SiO2, ZrO2, and ZrSiO4 attributable to the ZrB2/SiC particles, contributing to the enhancement of erosion resistance.Highlights Examines volume ratios of ZrB2/SiC. Discovers the best particle ratio (20%SiC, 80%ZrB2) for mechanical properties. Identifies the best particle ratio (30% SiC, 70% ZrB2) for erosion resistance. Reveals key phases enhancing erosion resistance with advanced analysis methods. Linear and mass ablation rate improved by 83% and 55% (best formation).

Study on the microstructure and mechanical properties of hot rolled nano-ZrB2/AA6016 aluminum matrix composites by friction stir processing

In this paper, in-situ ZrB2/AA6016 particle-reinforced aluminum matrix composites were prepared in molten A6016 aluminum alloy melt by KBF4-Al- K2ZrF6 reaction system. For the first time, this paper presents that after casting, the composites would be subjected to large strain hot rolling (LSHR) with 60 % undercutting and then friction stir processing (FSP) with a stirred probe speed of 1200 r/min and a traveling speed of 60 mm/min. To study the microstructure and mechanical properties of composites strengthened by large strain hot rolling combined with friction stir processing. The results show that the tensile strength of the base material is 140.1 MPa, the elongation is 46.3 %, the product of strength and elongation reaches 6.5 GPa%, and the average hardness is 43.4 HV; The tensile strength of LSHR+FSP nugget zone is 163.4 MPa, the elongation is 78.9 %, the product of strength and elongation reaches 12.9 GPa %, which is about 98.6 % higher than the base material, and the average hardness is 59.8 HV, which is about 37 % higher than the base material. SEM, EBSD, and TEM analyses showed that the average grain size is refined from 189.7 μm to 3.8 μm after LSHR+FSP. The ZrB2 particles are sufficiently fragmented, with a particle size of about 20 nm, and uniformly dispersed in the matrix. This study provides the theoretical and experimental basis for applying nanoscale ZrB2 particles reinforcing ultrafine crystalline aluminum matrix composites prepared by LSHR + FSP.

Microstructure and mechanical properties of Cu–Cr–Zr–ZrB2 composites by novel fabrication process of ultrasonic vibration treatment

Copper matrix composites with dual-scale particles were fabricated through casting with reaction. Ultrasonic vibration has been successfully introduced into the melt at about 1523 K while the microstructural development and mechanism of copper matrix composites with high-performance through a novel method of casting with ultrasonic vibration treatment are investigated. When ultrasonic vibration is applied, the distribution of micro-scale particles is greatly improved. Primary Cr phase convents to non-dendrite and large aggregates of ZrB2 particles are disrupted into small clusters because of acoustic cavitation and acoustic streaming. The ultimate tensile strength and elongation of Cu-1wt%Cr-0.3 wt%Zr-1wt%ZrB2 composite in as-cast state were 321 MPa and 14.37 %, recording a 28.4 % and 14 % increment respectively compared with the sample without treatment. After solution treatment, deformation and aging subsequently, the uniform distribution of reinforcements also decreases the average transverse grain thickness and increases the dislocation density which improve the comprehensive properties.

Dielectric resonance of composites containing randomly distributed ZrB2 particles with continuous dual-peak microwave absorption

Substantial efforts have been devoted to the elaborate component and microstructure design of absorbents (inclusions) in microwave absorbing (MA) composite materials. However, the mesoscopic architecture of composites also plays a significant role in prescribing their electromagnetic properties, which is rarely explored in studies of MA materials. Herein, a composite containing randomly distributed ZrB2 particles is fabricated to offer a mesoscopic cluster configuration, which produces dielectric resonance. The resonance disappears and reoccurs when ZrB2 is coated with insulating and semiconductive ZrO2 layers, respectively, suggesting that it is a plasmon resonance excited by electron transport between ZrB2 particles in clusters rather than any intrinsic resonance of the materials constituting the composite. The resonance strength can be regulated by controlling the quantity of electron transport between particles, which is accomplished by gradually increasing the insulating ZrO2-coated ZrB2 ratio, x, to disturb the electron transport in ternary disordered composites containing ZrB2 and insulating ZrO2-coated ZrB2. When x exceeds 0.7, the electron transport is cut off completely and the resonance thus disappears. The resonance induces double quarter-wavelength (1/4λ) interference cancellations or resonance absorption coupled with 1/4λ interference cancellation, giving rise to continuous dual-peak absorption. This work highlights the significance of mesoscopic architectures of composites in MA material design, which can be exploited to prescribe electromagnetic properties.

Enhanced mechanical properties and corrosion resistance of electro-deposited NiCoP composite coatings with ZrB2 particle addition

This work was initiated with the purpose of expanding the utilization of nickel-based composite coatings, especially in wear and corrosion-related industrial applications. NiCoP coatings have long attracted scientific and engineering interest due to their enhanced mechanical properties reinforced by incorporation with a reinforcement phase. In the present study, NiCoP composite coatings reinforced with ZrB2 ceramic particles were synthesized by direct current deposition using a modified Watt’s type bath. The microstructures of composite coatings were studied by x-ray diffraction analysis, energy dispersive x-ray spectroscopy, and scanning electron microscopy, respectively. The hardness and tribological properties of the composite coatings were evaluated and compared. The corrosion behaviors of the deposits were investigated using electrochemical spectroscopy and potentiodynamic polarization techniques in simulated seawater. The effect of ZrB2 content on the microstructures and mechanical properties of the composite coatings was explored and discussed. The present study indicates that there is a progressive enhancement in the hardness, corrosion resistance, and wear resistance of the composite coatings with the increase in ZrB2 loading. The NiCoP-12 g/l-ZrB2 coating possesses the highest microhardness and superior wear performance, while the NiCoP-6 g/l-ZrB2 coating exhibits the best anti-corrosion properties. The present study shows a cost-effective and feasible solution for the preparation of NiCoP protective coatings with enhanced properties, which holds great potential for industrial applications requiring wear and anti-corrosion protection.

Microstructure and properties of ZrB2-reinforced aluminum matrix composites consolidated by ECAP process

In this research work, the effects of mechanical alloying and subsequent compaction by ECAP on the microstructural, physical, and mechanical properties of Al-ZrB2 metal matrix composites (MMCs) were evaluated. To prepare composite powders, a mixture of Al and ZrB2 particles was mechanically alloyed at various times of 1, 6, 12, 18 and 24 h. SEM micrographs indicate that the size of the obtained particles decreases by increasing the time of mechanical alloying up to 18 h. However, after this time, increasing the time of mechanical alloying has led to an increase in the size of the particles. By means of mechanical alloying for 18 h, the average size of fine particles reached 823 nm, while coarse particles were 8 μm. The calculation via the use of XRD examination implies that the mean crystallite size of powder decreased from about 68 nm to 31 nm and 26.8 nm, for Al and Al-5%ZrB2 samples, respectively, while lattice strain increased from 0.25% to 0.64% and from 0.3% to 0.73% after 1 h to 24 h milling of same samples, respectively. However, the rate of crystallite size reduction after 12 h of mechanical alloying is gradually reduced, and that is reached its lowest level after 18 h. After that, increasing the time of mechanical alloying has led to a saturation in the lattice strain. In continue, the resulting composite powder was heated, consolidated and turned into bulk material by warm equal channel angular pressing (ECAP) at the temperature of 250 °C. The resultant optimum composite has been characterized by EDS elemental mapping. Microhardness measurements and shear punch tests were performed to evaluate the mechanical properties of the unreinforced and composite samples after the ECAP process. The Al-ZrB2 MMC bulk samples subjected to ECAP, with a ZrB2 amount of 5 wt%, had a relative density, hardness, and ultimate shear strength of 99.3%, 170 HV, and 151 MPa, respectively, using powders which have been mechanically alloyed up to 24 h.

Erosive wear and topographical study of zinc-aluminum based composite reinforced with in-situ formed ZrB2 particles

The present study deals with the erosive wear behaviour of a zinc-aluminum (ZA) alloy and composite in the slurry medium. The effects of reinforcement of zirconium diboride (ZrB2) particles in ZA alloy, as well as the impingement angle and duration of erosion wear responses have been studied. The slurry composition was prepared with 1.5 L of water and 500 g silica of a size range of 350–450 μm. The erosion tests are performed at a speed of 600 rpm for varying durations (20–80 h) and impingement angles (30°–90°). The erosive wear responses of the samples have been analyzed in terms of distinct features of their micro constituents like ZrB2 and the material removal mechanism in a prescribed set of conditions. A significant decrease in composite erosion compared to ZA alloy has been observed. With increased duration, both alloy and composite show increased erosive wear. Obtained results revealed that the composite shows 60–80 % less erosive wear than ZA alloy on operating conditions. The optimum results in wear have been observed at 45° for alloy and 60° for composite. Investigating topographical aspects using scanning electron microscopy and atomic force microscopy revealed that ZrB2 reinforcements resulted in smoother topography and reduced erosive wear.

Hydrophobic Coating on Metal Matrix Composites

Abstract: The combination of traditional aluminum metal matrix composites (MMCs) with innovative reinforcement materials offers promising avenues for enhancing material properties and expanding application domains. In this study, aluminum matrix composites reinforced with ZrB2 (zirconium diboride) particles were fabricated using a stir casting technique. The addition of ZrB2 to the aluminum matrix aimed to improve mechanical strength, wear resistance, and thermal stability. Following fabrication, the resulting composite specimens were subjected to a surface modification process involving the application of a superhydrophobic coating. The superhydrophobic coating, characterized by its extreme water repellency and self-cleaning properties, was applied to the surface of the aluminum-ZrB2 composites using a spray-coating method. The coating material consisted of a hydrophobic compound integrated with nanostructured particles, engineered to achieve a hierarchical surface morphology that mimics natural superhydrophobic surfaces. The coated specimens were evaluated for their water repellency, contact angle measurements, and durability under various environmental conditions. The results of this study demonstrated that the combination of aluminum metal matrix composites with ZrB2 reinforcement, coupled with the application of a superhydrophobic coating, yielded surfaces with exceptional water-repellent properties. The coated composites exhibited high contact angles and low water adhesion, indicative of their superhydrophobic nature. Furthermore, the durability tests revealed the robustness of the coating against mechanical abrasion and environmental exposure. Overall, the integration of aluminum-ZrB2 composites with a superhydrophobic coating holds significant promise for applications requiring water-resistant surfaces, suchas aerospace components, marine structures, and outdoor equipment. This researchcontributes to advancing the development of multifunctional materials with tailoredsurface properties, paving the way for improved performance and longevity in diverse engineering applications

High temperature friction and wear behavior of Mo–Si–B/ZrB2 composites

The Mo–Si–B alloys with good wear resistance are prominent for high-temperature applications. In this work, the effects of ZrB2 content and test temperature on the tribological properties of the Mo–Si–B/ZrB2 composites at 25–800 °C were investigated. It indicates that the composites show an enhanced wear resistance, which can be ascribed to the improved hardness and formation of Zr-rich borosilicate layer by introducing ZrB2 particles. The main wear mechanism is abrasive wear accompanies with adhesive wear at 25–400 °C, where ZrB2 addition can reduce the wear loss. And adhesive wear dominates at 600–800 °C, where the formed tribo-layer can provide a good self-lubricity and is beneficial for improving the wear resistance of the composites.

Green Microwave-Assisted Cladding: Enhancing SS-304 with Ni-ZrB2 Composite Coatings

This study focuses on achieving effective deposition of a Ni and 15% ZrB2 particle mixture onto SS-304 substrate surfaces through meticulous preparation steps. Thorough cleaning of the SS-304 substrate using alcohol in an ultrasonic bath eliminated contaminants, ensuring optimal adhesion. Simultaneously, the Ni-ZrB2 mixture underwent preheating at 1200°C for 20 hours in a muffle furnace to eliminate moisture content, crucial for preventing coating defects. Uniform distribution of the preheated powder onto the substrate was crucial for consistent coating thickness. Microwave hybrid heating (MHH) using charcoal as a susceptor material overcame microwave reflection by rapidly heating the powder mixture. SEM analysis revealed a uniform dispersion of both Ni and ZrB2 particles across the substrate surface, indicating successful deposition and optimal adhesion. The cladding resulted in a significant improvement in surface hardness, with an increase of approximately 42.43%. The wear rate, measured at 0.00178 mm³/m, and the coefficient of friction, determined to be 0.246, provided crucial insights into the surface’s wear resistance and frictional behavior, confirming its suitability for applications requiring enhanced durability and performance. These findings highlight the efficacy of the microwave-assisted cladding process in enhancing SS-304 with Ni-ZrB2 composite coatings, paving the way for its utilization in various industrial applications.

Enhancing Aluminum-Based Composite Manufacturing: Leveraging ZrB2 Reinforcement via Friction Stir Process

This study investigates the enhancement of aluminum-based composite manufacturing through the utilization of ZrB2 reinforcement via Friction Stir Process (FSP). Achieving a uniform distribution of ZrB2 particles is crucial for optimizing material properties. The addition of ZrB2 nanoparticles using FSP has led to notable improvements in various mechanical properties of aluminum. Tensile strength increased by 20.25%, hardness by 35.67%, fatigue strength by 23.67%, and wear resistance by 29.45%. These enhancements underscore the effectiveness of nanoparticle reinforcement in fortifying aluminum matrices against mechanical stresses and wear mechanisms. The results demonstrate the potential of FSP-based techniques in tailoring the mechanical properties of aluminum-based composites for diverse applications. This research contributes valuable insights into advanced manufacturing methods for developing high-performance materials with enhanced mechanical characteristics, facilitating the advancement of aluminum composite technologies for industries requiring superior strength, durability, and wear resistance.

Effect of in-situ ZrB2 nanoparticles on microstructure and mechanical properties of friction stir welding joints in 7N01 matrix composites

In this paper, in-situ nanoparticles ZrB2 were introduced to improve the mechanical properties of Friction Stir Welding (FSW) joints in 7N01 matrix composites. The recrystallization driving force was increased induced by ZrB2 particles. Modified by ZrB2 nanoparticles, the grains in the SZ (stir zone) were refined from 4.8 μm (7N01) to 3.7 μm (ZrB2/7N01), and the recrystallization proportion was increased from 75.1% (7N01) to 85.4% (ZrB2/7N01). Compared with the 7N01 matrix, the ultimate tensile strength (UTS) of friction stir welding joints in ZrB2/7N01 composites was enhanced from 283.3 to 395.6 MPa, the yield strength (YS) was enhanced from 250.8 to 361.4 MPa, elongation was enhanced from 12.7% to 16.2%. The strengthening effect was mainly achieved through the Orowan mechanism. The MgZn2 precipitates grew up under the influence of heat input, the inhibiting effect of precipitates on dislocations movement was weakened. Nanosized ZrB2 particles with superior coarsening resistance can still maintain its morphology and size at high temperature, playing a good strengthening role during the FSW.

Synergistic reinforcement of in situ ZrB2 particles and Sc on the corrosion behaviour of 7N01 alloy

In this study, the effects of in situ ZrB2 particles and rare earth element Sc on the corrosion behavior of 7N01 alloy were investigated separately, with the characteristics of their synergistic enhancement being elucidated. The introduction of Sc into the ZrB2/7N01 composites led to an enhancement in both the distribution and morphology of the in situ particles, with the size of ZrB2 particles being significantly reduced and large particle clusters almost disappearing compared to the situation without Sc addition. A decrease in the grain size of the matrix alloy 7N01 from 170 μm to 33 μm was also observed when the Sc addition was 0.5 wt%. The low corrosion susceptibility observed after the addition of Sc was attributed to the refinement of grains and the inhibition of the formation of precipitate-free zones. The addition of ZrB2 improved corrosion resistance by promoting the precipitation of Al3Sc precipitates. Importantly, it was found that the 7N01 alloy with 3 wt% ZrB2 and 0.5 wt% Sc exhibited high mechanical properties and admirable corrosion resistance, which makes it a promising material for various applications. In summary, this study highlighted the individual and combined effects of in situ ZrB2 particles and rare earth element Sc on the corrosion behavior of 7N01 alloy, with valuable insights being provided for the development of advanced structural composite materials.

Effects of hot deformation and in-situ ZrB2 particle on microstructure and tensile performance of AA7085 composite sheets

Effects of hot deformation and in-situ ZrB2 particle on microstructure and tensile performance of AA7085 composite sheets

Effect of Sc on the microstructure and mechanical properties of ZrB2 particles reinforced spray formed 7055 aluminum alloy TIG welded joint

Adding nano ceramic particles to the weld seam is an effective way to improve the strength of the spray formed 7055 aluminum alloy welded joint. However, nano ceramic particles are prone to agglomeration, and the agglomerated nano ceramic particles in welded joint can cause stress concentration and brittle fracture of the specimen. In order to improve the aggregation of nano ZrB2 ceramic particles in the weld seam and further improve the mechanical properties of spray formed 7055 aluminum alloy TIG welded joint, Sc/ZrB2-7055 (SZ7) and ZrB2-7055 (Z7) welded joints were prepared in this study. Compared to the Z7 weld seam with coarse grains and severe aggregation of ZrB2 particles, the SZ7 weld seam has fine grains, and the distribution of ZrB2, Al3(Sc, Zr), and Sc modified ZrB2 particles in the weld seam was more uniform. The tensile strength and elongation of Z7 welded joints were 281 MPa and 2.0%, while the tensile strength and elongation of SZ7 welded joints were 320 MPa and 4.9%. The tensile strength and elongation values of SZ7 welded joints have increased by 13.8% and 145% respectively compared to Z7 welded joints. Sc elements formed a rich Sc layer on the surface of ZrB2 particles, which passivated the sharp corners of ZrB2 particles and increased the wettability between ZrB2 particles and Al liquid, resulting in uniform distribution of ZrB2 particles in the weld seams. Fine grain strengthening, dispersion strengthening, and dislocation strengthening are the main reasons for improving the mechanical properties of SZ7 welded joints.

Investigation on the high strength and improved creep behavior of in-situ (Al2O3+ZrB2)/7055 Al nanocomposites

In this paper, 7055 Al composites reinforced by Al2O3 and ZrB2 nanoparticles were fabricated by in-situ reaction. The adhesion (Wad) of the ZrB2/Al interface was 3.91 J/m2 while the adhesion at the Al2O3/Al interface was 3.69 J/m2. At room temperature and high temperature up to 523 K, yield strength (YS), ultimate tensile strength (UTS), and elongation (EI) in (Al2O3+ZrB2)/7055 Al composites reached up to 595 MPa, 710 MPa, 19% and 371 MPa, 435 MPa, 24%, respectively. The combined strengthening effect produced by Al2O3 and ZrB2 nanoparticles was found to be stronger than that of the individual ZrB2 particles and the matrix. In addition, the steady creep rate of the (Al2O3+ZrB2)/7055 Al composites were the lowest, constituting only 3∼14% of the matrix and 5∼68% of the ZrB2/7055 Al composites. The true stress exponents in the matrix and composites were 5, indicating a dominative dislocation climbing mechanism. Both the promotion of precipitation nucleation and the precipitation-coarsening inhibition during the creep process at the interfaces between the matrix and nanoparticles were discussed. Additionally, deformed and fragment mechanisms and the creep resistance mechanism were elucidated.