The study examines the effect and mechanism of 3Y-ZrO2 addition on the phase composition, microstructure, and mechanical properties of Al2O3-ZrO2 ceramics. The ceramics were sintered at 1580 degrees C for 120 min, comprising varying proportions of 20, 40, 60, and 80 wt.% of 3Y-ZrO2. The study investigates the phase composition, phase content, microstructure, relative density, microhardness, fracture toughness, and wear rate of the ceramics. Notably, Al2O3-ZrO2 ceramics demonstrated a dense surface with evenly distributed reinforcing particles in the matrix. The microhardness and wear rate of Al2O3-ZrO2 ceramics declined with increased 3Y-ZrO2 addition; in contrast, the bending strength, abrasion resistance, and fracture toughness increased with the addition of 3Y-ZrO2. Alumina grain refinement, crack propagation inhibition, and microcrack toughening induced by tetragonal-to-monoclinic phase transformation are the primary factors influencing these changes. Meanwhile, as the content of 3Y-ZrO2 increases, the fracture mode of Al2O3 shifted gradually from transgranular to intergranular, whereas ZrO2 maintained predominantly transgranular fracture.

In this work, the 3D-SiCp/A356 composites with interpenetrating microstructure were prepared by pressure infiltration of A356 aluminum alloy into a porous 3D-SiC ceramic preform, which served as reinforcement. The effects of the surface oxidation treatment of the SiC particles on microstructure, thermal expansion coefficient, and bending strength of as-fabricated composites were investigated. The results revealed that the initial structure of the 3D-SiC ceramic preform could be retained after pressure infiltration, the pores of the preform were filled with A356 aluminum alloy, and the particles were uniformly distrib-uted in the A356 matrix alloy. The thermal expansion coefficient of the SiC/A356 composite reinforced by oxidized SiC particles was lower than that of the unoxidized SiC particle -reinforced composite. It increased with increasing temperature for both, eventually reaching maxima at 420 & DEG;C and 350 & DEG;C, respectively, and decreased thereafter. However, a rapid decrease in the thermal expansion coefficient was evident at 565 & DEG;C because of the over-burning of the A356 aluminum matrix. In particular, the surface oxidation treatment of SiC particles changed the nature of bonding between SiC and Al, which reduced the strength of the composites. As a result, the bending strength of the unoxidized SiC particle -reinforced composite was approximately twice that of the oxidized SiC particle-reinforced composite. Additionally, the bending strength values of the SiC-Al showed an obvious anisotropic behavior. The bending strength measured by loading parallel to the infiltration direction was 2.5 times larger than that of a perpendicular loading.& COPY; 2023 The Authors. Published by Elsevier B.V. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/).

h-BN is a two-dimensional ceramic material with a lamellar structure, known for its typical orientation char-acteristics on mechanical and thermal properties. By optimizing the size and arrangement of h-BN grains in the matrix, the anisotropic characteristics of h-BN ceramics can be fully utilized to obtain ceramic materials with high thermal conductivity or high strength. In order to study the effect of grain orientation distribution on the mechanical and thermal properties of materials, the index of orientation distribution (IOP) was used to quan-titatively characterize the orientation degree of h-BN grains and analyzed the effect of h-BN grain size on ma-terial properties. The results show when the initial h-BN size is 13.50 mu m, the ceramic has the highest orientation degree/-507, and the mechanical and thermal properties show obvious anisotropy. While the related properties of BN-YAG ceramics varies significantly with the decrease of initial h-BN grain size.

铝基多孔复合材料由铝基体和空心微球复合而成,兼具轻质与吸能特性.本文采用放电等离子烧结(SPS)方法制备玻璃空心微球/铝基多孔复合材料,通过光学显微镜、SEM、准静态压缩原位观察和数字图像相关技术表征,分析了空心微球含量及尺寸对复合材料准静态压缩变形行为和吸能性能的影响.结果表明:两步升温SPS烧结制备所得的铝基多孔复合材料,其微球弥散均匀嵌于铝基体中,铝基体熔合致密.随空心微球含量增加,复合材料压缩应力整体降低,屈服平台区扩大但由平滑转变为锯齿状,压缩变形行为从较均匀的鼓状形变逐渐发展为脆性剪切,微球体积分数为 50vol%的多孔复合材料吸能能力为 23.6 J·cm-3,高于体积分数为 30vol%和 70vol%的多孔复合材料,复合材料吸能能力与微球含量间存在最优对应关系.小尺寸微球具有更好的抗压能力,随小尺寸微球占比的提高,复合材料微观上可承受更高的应力-应变集中,宏观上剪切形变的压缩应变增大,本文中小尺寸微球多孔复合材料的峰值应力和吸能能力分别为 89.4 MPa和29.0 J·cm-3,与大尺寸微球多孔复合材料相比分别提高23.5%和22.9%.

The glass cenosphere/Al syntactic foam core sandwich with steel and aluminum sheets was successfully synthesized using the spark plasma sintering method, it owns metallurgical interfaces between the foam core and the metal sheets. The aluminum foil placement between the glass cenosphere-aluminum mixture powder and steel sheet in the preparing process facilitated the Fe-Al diffusion to form a double-layer reaction metallurgical interface containing Fe4Al13 and Fe2Al5. While for the foam core-aluminum sheet, an excellent fusion of aluminum was achieved at the interface. Both foam core-steel sheet and foam core-aluminum sheet showed good interfacial shear strength. There is a significant difference in the interfacial shear behavior between the foam core-steel sheet and the foam core-aluminum sheet due to their different metallurgical interfaces. The stable fusion of aluminum at the foam core-aluminum sheet interface can be conducive to the interfacial load transfer, resulting in a better interfacial bonding than that of the foam core-steel sheet.

采用模压成形工艺结合压力浸渗法制备了SiC/A356 Al复合材料,利用XRD、SEM和EDS等分析了SiC颗粒氧化处理前后的物相组成、组织形貌及粒度分布,研究了原始/氧化SiC颗粒对复合材料界面组织、抗弯强度、线膨胀系数及热导率的影响;通过SEM分析了该复合材料的断口形貌,并探讨了其断裂机制.结果表明,采用该方法可获得颗粒均匀分散、界面洁净、接近全致密的SiC/A356 Al复合材料.表面氧化处理包覆在SiC颗粒表面的SiO2能够有效抑制Al4 C3脆性相的生成,但也使得SiC与A356之间由化学反应结合转变为冶金结合,导致复合材料的弯曲强度大幅降低,线膨胀系数略有降低,同时复合材料的热导率显著提高.氧化SiC颗粒增强的复合材料的抗弯强度是增强相为原始SiC颗粒的复合材料1/2左右,线膨胀系数在30～350℃范围内仅降低了(0.59～0.99)×10-6 K-1,热导率提高了42.86％.

Hexagonal boron nitride (h-BN) has a typical two-dimensional flake structure, so the anisotropy of h-BN grains caused by directional arrangement cannot be ignored when studying the thermal vibration resistance of materials under thermal cycling. In this paper, h-BN-matrix textured ceramics prepared with different holding time were selected, and the effects of thermal vibration temperature difference and thermal cycles on the phase and thermal vibration resistance of h-BN-matrix textured ceramics were studied. The results show that under the condition of high-frequency thermal cycling, the residual strength ratio (RSR) of BN-based textured ceramics is closely related to the holding time and showing obvious anisotropy. At the same time, there is a thermal vibration temperature range in which the internal stress will change from relief to re-accumulation.

Phosphate/borate antioxidant compound was successfully prepared on a graphite substrate by the impregnation method with subsequent heat-treatment. The impregnated graphite exhibited higher oxidation resistance than the untreated graphite in static air at 500 degrees C up to 50 h. H3PO4, H3BO3, Al(H2PO4)(3), and Na2B4O7 center dot 10H(2)O in the antioxidant compound formed an excellent chemically and thermally stable BPO4 through the polymerization reaction during the heat-treatment to seal in the pores on the graphite surface. Additionally, during the oxidation process, the B2O3 formed by the decomposition of the remaining H3BO3 and the Al2O3 formed by the reaction of Al-ions with oxygen could further block the oxidation channels, effectively inhibiting the combination of carbon and oxygen. In summary, the synergistic effect of BPO4, B2O3, and Al2O3 anti-oxidative products together improved the oxidation resistance of the impregnated graphite.

AlN/(Ti, W)/Cu substrates were successfully fabricated by the combination of magnetron sputtering and electroless copper plating, exhibited layered distribution without obvious defects or delamination. The adhesion film in AlN/Ti/Cu was composed of TiN, Al, and Ti crystallites due to the reaction between the sputtered Ti layer and the AlN substrate, while in AlN/W/Cu was α-W and β-W crystallites with a mixed distribution but a thin W-rich amorphous layer at the interface towards Cu contact. In AlN/TiW/Cu was W-rich TixW1−x and α-Ti with the interlayer distribution. The scratch failure of the AlN/(Ti, W)/Cu substrates included the peeling of the Cu plating layer and adhesion film. The nanoscale hard phase layered combination of the adhesion film in AlN/TiW/Cu exhibited better peeling resistance, resulting in the most prominent adhesion strength among the substrate system. The existence of an amorphous layer in AlN/W/Cu led to the lower thermal conductivity. AlN/TiW/Cu substrate showed good comprehensive properties including adhesion strength and thermal conductivity.

Glass microspheres are considered to be suitable fillers in syntactic foams due to their high specific strength, however, it's evidently easy to react with Al-Mg alloy or Mg alloy. A surface protection coating MgO were successfully prepared on microspheres using sol-gel method. The crystallization process and coating effect of MgO with different molar ratio acetic acid complexant in sol compositions were studied. The dried gels were dehydrated and polycondensed to form magnesium acetate and finally turned to be stable MgO after annealing at 400 degrees C. The MgO coatings, with small particles after annealing, successfully modified the surface of microspheres when the sol composition (molar) magnesium acetate hydrate/ acetic acid/dry ethanol was 1:6:29. The MgO coating has inhibited the excessive interfacial reaction between the glass microspheres and the Al-Mg alloy matrix in syntactic foam which the reasons have been discussed. (C) 2019 Elsevier B.V. All rights reserved.

Aluminum matrix composites represent a potential application prospect in the field of electronic packaging.In order to obtain high volume fraction of aluminum matrix composites,high volume fraction SiC particle reinforced A356 matrix composites (SiCp/A356)was prepared by pressure infiltration method.The phase,microstructure and conductivity of the composites were cha-racterized by metallographic microscope,XRD,SEM and EDS.The results demonstrates that the SiCp/A356 composites prepared by this method have compact structure,the SiC particles are uniformly distributed in the A356 matrix and the interface is better.Moreo-ver,the interfacial reaction is well controlled.As a result,some harm phases especially Al4C3 fragility phase are nearly absent from interfacial reaction products.A layer of SiO2 formed from SiC after particle surface oxidation treatment.The SiO2 thin films were formed on the surface of the particles,which could inhibit the interfacial reaction.However,the shrinkage of the composites re-duced,the resistivity of the composites increased,and the conductivity of the composite materials became worse.

The effect of titanium and vanadium on the microstructure and mechanical properties of hypereutectic high-chromium cast iron was investigated.The results show that the niobium can neither refine primary carbides nor refine eutectic carbides.The primary M7C3 carbides and eutectic carbides could be refined obviously with the increase of titanium content.The hardness of primary carbides and eutectic carbides increases with the increase of titanium content,and the impact toughness changes little.The wear resistance of high-chromium cast iron increases with the increase of titanium content.

The failure behavior of ball mill liner in copper mine under wet grinding conditions was analyzed.The microstructure of failure lining plate was analyzed by optical microscope,scanning electron microscope,energy dispersive spectroscope,hardness tester and other analysis methods.The corrosion resistance,mechanical properties and corrosive wear mechanism of the Cr-alloy steel in weak acid condition have also been characterized by electro-chemical polarization,tensile and impacting testing.The resuit shows that the liner material presents the satisfied corrosion resistance in the static simulation copper slurry.However,the dynamic impact wear of copper mine slurry greatly reduces the corrosion resistance of the material.Failure modes of lining plates are characterized by cutting furrows,corrosion pits and peeling pits,and the interaction of corrosion and wear is responsible for liner failure.

The SiC particle preform was prepared by 3D printing,and the SiC reinforced A356 matrix composites(SiCp/A356 composites) were prepared by pressure infiltration technology.The microstructure and phase of SiCp/A356 composites were analyzed by optical microscope (OM),scanning electron microscope (SEM),energy dispersive spectroscope (EDS),X-ray diffraction(X-ray) and other modern analysis methods.The results reveal that the microstructure of SiCp/A356 composites fabricated by above-mentioned methods exhibits compact with uniformly distributed SiC particles in the A356 matrix and the desirable interface bonding.Moreover,the interfacial reaction is well controlled.As a result,some harmful phases such as Al4C3 brittle phase are absent from interfacial reaction products.Elements Si in the A356 alloy can prevents the formation of Al4C3 brittle phase,and the existence of Mg in the A356 alloy can improve significantly the wettability of SiC with A356.