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1.
Submicrometer Al2O3 composites with more than 20 vol.% of SiC particles were produced using a multiple infiltration of porous bodies with a liquid polymer SiC precursor. The fully dense composites were successfully densified using a sinter-HIP process. Parameters of sintering and HIP steps are discussed with respect to both densification and microstructure evolution of the composites. The initial pressure during the sintering step plays an important role for the preparation of fully dense composites with a submicrometer alumina matrix at 1750 °C. Optimized densification schedule of sinter-HIP represents a novel approach of densification at relatively mild conditions compared to previously reported or common densification methods of Al2O3–SiC composites with high SiC content, such as pressureless sintering, hot pressing and post-HIPing. The method expands the possibilities for preparation of alumina based composites with SiC volume fraction > 20 vol.%, filling the gap in available literature data.  相似文献   

2.
The magnesium matrix composites reinforced with three volume fractions (3, 5 and 10 vol.%) of submicron-SiC particles (∼0.5 μm) were fabricated by semisolid stirring assisted ultrasonic vibration method. With increasing the volume fraction of the submicron SiC particles (SiCp), the grain size of matrix in the SiCp/AZ31B composites was gradually decreased. Most of the submicron SiC particles exhibited homogeneous distribution in the SiCp/AZ31B composites. The ultimate tensile strength and yield strength of the 10 vol.% SiCp/AZ31B composites were simultaneously improved. The study of interface between the submicron SiCp and the matrix in the SiCp/AZ31B composite suggested that submicron SiCp bonded well with the matrix without interfacial activity.  相似文献   

3.
The effect of titanium additions on the interface and mechanical properties of infiltrated Cu8 wt%Al–Al2O3 composites containing 57 ± 2 vol% ceramic are investigated, exploring two different Al2O3 particle types and four different Ti concentrations (0, 0.2, 1, 2 wt%Ti). Addition of 0.2 wt%Ti leads to the development of a thin (5–10 nm) layer enriched in Ti at the interface between Cu alloy and Al2O3 particles; this Ti concentration produces the best mechanical properties. With higher Ti-contents Ti3(Cu, Al)3O appears; this decreases both the interface and composite strength. Composites reinforced with vapor-grown polygonal alumina particles show superior mechanical properties compared to those reinforced by angular comminuted alumina particles, as has been previously documented for aluminum-based matrices. Micromechanical analysis shows that damage accumulation is more extensive, as is matrix hardening by dislocation emission during composite cooldown, in the present Cu8 wt%Al matrix composites compared with similarly reinforced and processed Al-matrix composites.  相似文献   

4.
Nano/micrometer hybrids are prepared by chemical vapor deposition growth of carbon nanotubes (CNTs) on SiC, Al2O3 and graphene nanoplatelet (GNP). The mechanical and self-sensing behaviors of the hybrids reinforced epoxy composites are found to be highly dependent on CNT aspect ratio (AR), organization and substrates. The CNT–GNP hybrids exhibit the most significant reinforcing effectiveness, among the three hybrids with AR1200. During tensile loading, the in situ electrical resistance of the CNT–GNP/epoxy and the CNT–SiC/epoxy composites gradually increases to a maximum value and then decreases, which is remarkably different from the monotonic increase in the CNT–Al2O3/epoxy composites. However, the CNT–Al2O3 with increased AR  2000 endows the similar resistance change as the other two hybrids. Besides, when AR < 3200, the tensile modulus and strength of the CNT–Al2O3/epoxy composites gradually increase with AR. The interrelationship between the hybrid structure and the mechanical and self-sensing behaviors of the composites are analyzed.  相似文献   

5.
Ultra-fine grained γ-Ni–xFe (x = 20, 50, and 64 (nominal)) dispersed Al2O3-matrix composites were fabricated by a mechano-chemical process plus hot-pressing, and their mechanical and magnetic properties were explored. The results indicated that all composites incorporated with different γ-Ni–xFe alloys possessed high densities (relative density D  98%) and sub-micrometer-sized matrix dispersed with γ-Ni–xFe particles of sizes below ∼500 nm. As compared to other two composite systems, γ-Ni–20Fe/Al2O3 had finer microstructures and displayed superior fracture toughness and strength. In high iron-contained γ-Ni–64Fe/Al2O3 composite undesired FeAl2O4 phase formed on the matrix grain boundaries, which is mainly responsible for its inferior mechanical properties. Although Young’s modulus and hardness of Ni–20Fe/Al2O3 composite system decreased, its fracture toughness increased monotonously with increasing the alloy content in the composition range investigated. Moreover, incorporation of ferromagnetic γ-Ni–xFe particles led all the composite systems to display ferromagnetism with their saturation magnetization increasing almost linearly with increasing alloy content. In addition, experiments showed that their ferromagnetism had high thermal stability (Tc = ∼580 °C), no obvious magnetism degradation and magnetic interactions of the alloys with the matrix being observed. The combination of good mechanical properties with excellent magnetic performance would make this material be very valuable in industry.  相似文献   

6.
This paper presents the method for measurement of the adhesion force and fracture strength of the interface between ceramic particles and metal matrix in ceramic reinforced-metal matrix composites. Three samples with the following Cu to Al2O3 ratio (in vol.%) were prepared: 98.0Cu/2.0Al2O3, 95.0Cu/5.0Al2O3 and 90Cu/10Al2O3. Furthermore, microwires which contain a few ceramic particles were produced by means of electro etching. The microwires with clearly exposed interface were tested with use of the microtensile tester. The microwires usually break exactly at the interface between the metal matrix and ceramic particle. The force and the interface area were carefully measured and then the fracture strength of the interface was determined. The strength of the interface between ceramic particle and metal matrix was equal to 59 ± 8 MPa and 59 ± 11 MPa in the case of 2% and 5% Al2O3 to Cu ratio, respectively. On the other hand, it was significantly lower (38 ± 5 MPa) for the wires made of composite with 10% Al2O3.  相似文献   

7.
《Composites Part A》1999,30(4):425-427
Ceramic nanocomposites, Si3N4 matrix reinforced with nano-sized SiC particles, were fabricated by hot pressing the mixture of Si3N4 and SiC fine powders with different sintering additives. Distinguishable increase in fracture strength at low and high temperatures was obtained by adding nano-sized SiC particles in Si3N4 with Al2O3 and/or Y2O3. Si3N4/SiC nanocomposite added with Al2O3 and Y2O3 demonstrated the maximum strength of 1.9 GPa with average strength of 1.7 GPa. Fracture strength of room temperature was retained up to 1400 as 1 GPa in the sample with addition of 30 nm SiC and 4 wt% Y2O3. Striking observation in this nanocomposite is that SiC particles at grain boundary are directly bonded to Si3N4 grain without glassy phases. Thus, significant improvement in high temperature strength in this nanocomposite can be attributed to inhibition of grain boundary sliding and cavity formation primarily by intergranular SiC particles, besides crystallization of grain boundary phase.  相似文献   

8.
A zirconia/alumina nanocomposite stabilized with cerium oxide (Ce-TZP/Al2O3 nanocomposite) can be a good substitute as reinforcement in metal matrix composites. In the present study, the effect of the amount of 10Ce-TZP/Al2O3 particles on the microstructure and properties of Al/(10Ce-TZP/Al2O3) nanocomposites was investigated. For this purpose, aluminum powders with average size of 30 μm were ball-milled with 10Ce-TZP/Al2O3 nanocomposite powders (synthesized by aqueous combustion) in varying amounts of 1, 3, 5, 7, and 10 wt.%. Cylindrical-shape samples were prepared by pressing the powders at 600 MPa for 60 min while heating at 400–450 °C. The specimens were then characterized by scanning and transmission electron microscopy (SEM and TEM) in addition to different physical and mechanical testing methods in order to establish the optimal processing conditions. The highest compression strength was obtained in the composite with 7 wt.% (10Ce-TZP/Al2O3) sintered at 450 °C.  相似文献   

9.
《Materials Research Bulletin》2003,38(9-10):1509-1517
Mechanical properties of in-situ toughened Al2O3/Fe3Al nano-/micro-composites were measured. Effects of Fe3Al content, sintering temperature and holding time on properties and microstructure of the composites were investigated. The addition of Fe3Al nano-particles decreased the aspect ratio and grain size of Al2O3, and changed the fracture mode of composites. The maximum bending strength and fracture toughness were 832 MPa and 7.96 MPa m1/2, which were obtained in Al2O3/5 wt.% Fe3Al sintered at 1530 °C and Al2O3/10 wt.% Fe3Al sintered at 1600 °C, respectively. Compared to monolithic alumina, the strength increased by 132% and the toughness increased by 73%. The improvement in the mechanical properties of the composites was attributed to the change in fracture mode from intergranular fracture to transgranular fracture, the “in-situ reinforced effect” arising from the platelet grains of Al2O3 matrix, refined microstructure by dispersoids, as well as crack deflection and bridging of intergranular and intragranular Fe3Al.  相似文献   

10.
Three kinds of A356 based composites reinforced with 3 wt.% Al2O3 (average particle size: 170 μm), 3 wt.% SiC (average particle size: 15 μm), and 3 wt.% of mixed Al2O3–SiC powders (a novel composite with equal weights of reinforcement) were fabricated in this study via a two-step approach. This first process step was semi-solid stir casting, which was followed by rolling as the second process step. Electroless deposition of a copper coating onto the reinforcement was used to improve the wettability of the ceramic particles by the molten A356 alloy. From microstructural characterization, it was found that coarse alumina particles were most effective as obstacles for grain growth during solidification. The rolling process broke the otherwise present fine silicon platelets, which were mostly present around the Al2O3 particles. The rolling process was also found to cause fracture of silicon particles, improve the distribution of fine SiC particles, and eliminate porosity remaining after the first casting process step. Examination of the mechanical properties of the obtained composites revealed that samples which contained a bimodal ceramic reinforecment of fine SiC and coarse Al2O3 particles had the highest strength and hardness.  相似文献   

11.
Directionally solidified ternary Al2O3/Y3Al5O12(YAG)/ZrO2 hypoeutectic rod composites were successfully fabricated by the laser zone remelting technique. The microstructure and mechanical properties of the composite were investigated. The microstructure presented a complex three-dimensional network structure consisting of fine Al2O3 (41 vol.%) and YAG (49 vol.%) phases, with smaller ZrO2 (10 vol.%) phases partially distributed at the Al2O3/YAG interfaces. The irregular growth behavior in the hypoeutectic was revealed. The hardness and fracture toughness at ambient temperature were measured to be 17.3 GPa and 5.2 MPa m1/2, respectively. The toughness enhancement in comparison with previous binary Al2O3/YAG composites was mainly attributed to the refined microstructure, and crack deflection, branching and bridging. Moreover, the residual stresses, generated by different thermal expansion coefficients of the component phases, also importantly contributed to the improved toughness. Correlations between the addition of the third component ZrO2 and the microstructure and properties were discussed as well.  相似文献   

12.
Some important problems associated with cast metal matrix composites (MMCs) include non-uniformity of the reinforcement particles, high porosity content, and weak bonding between reinforcement and matrix, which collectively result in low mechanical properties. Accumulative roll bonding (ARB) process was used in this study as a very effective method for refinement of microstructure and improvement of mechanical properties of the cast Al/10 vol.% Al2O3 composite. The average particle size of the Al2O3 was 3 μm. The results revealed that the microstructure of the composite after eleven cycles of the ARB had an excellent distribution of alumina particles in the aluminum matrix without any noticeable porosity. The results also indicated that the tensile strength and elongation of the composites increased as the number of ARB cycles increased. After eleven ARB cycles tensile strength and elongation values reached 158.1 MPa and 7.8%, which were 2.54 and 2.36 times greater than those of the as-cast MMC, respectively.  相似文献   

13.
Magnesium composites of AZ31–Al2O3–Cu formulations were produced using the disintegrated melt deposition technique following by hot extrusion. Microstructural characterization showed reasonable distribution of secondary phases up to 1 vol.% of copper. A tendency to form clustered agglomeration and longer shape of secondary phases was observed when the amount of copper was increased to 1.5 vol.%. Mechanical tests indicated remarkable improvements in 0.2%YS, UTS and microhardness when nano-alumina and sub-micron copper were added into AZ31. The ductility was increased up to 9.3% in the case of AZ31–1.5Al2O3–1.0Cu sample and significantly reduced (5.5%) when the amount of copper was increased to 1.5 vol.%. Heat treated sample of AZ31–1.5Al2O3–1.0Cu showed overall improvement in both tensile strength and ductility. The results suggest that the judicious selection of composition and heat treatment has the capability to enhance overall tensile response of Mg–Al2O3–Cu nanocomposites.  相似文献   

14.
《Materials Letters》2006,60(13-14):1651-1653
TiAl-based specimens were siliconized with two different kinds of cementation respectively, one is 23 vol.% Si + 77 vol.% Al2O3, and the other is 23 vol.% Si + 77 vol.% ZrO2. SEM observation showed that a Ti5Si3-based layer, in which some Al2O3 particles dispersed, formed on the surface after siliconization. Further observation showed that an extra outer Al2O3 layer existed on the surface of specimens siliconized with 23 vol.% Si + 77 vol.% Al2O3, while no such Al2O3 layer was found in specimens siliconized with 23 vol.% Si + 77 vol.% ZrO2. The cyclic oxidation test performed at 900 °C shows that the oxidation resistance was significantly improved by siliconizing. By comparison, the specimens that siliconized with 23 vol.% Si + 77 vol.% Al2O3 exhibits a better oxidation resistance than that with 23 vol.% Si + 77 vol.% ZrO2. It was deduced that the extra outer Al2O3 layer is beneficial to the oxidation resistance of siliconized TiAl-based alloy.  相似文献   

15.
In this study, Al2O3 particles were employed to improve the microstructure of LM24 and therefore, to increase the yield strength and tensile strength of this kind of alloy. In situ Al2O3 particles were obtained by direct reaction between oxygen and Al melt at 750–800 °C. Microstructure examination shows that the size of in situ formed Al2O3 particles was about 1–2 μm, and interestingly, with addition of in situ Al2O3 particles, the coarse primary Si phase was disappeared completely. More important, the yield strength and the tensile strength of Al2O3/LM24 are increased by 52 MPa, 16 MPa than that of LM24 alloy with 0.1% Sb addition. The value of 181 MPa and 315 MPa is for yield strength and tensile strength of Al2O3/LM24 respectively. Besides, the yield strength and tensile strength are 180 MPa and 314 MPa respectively for Al2O3/LM24 alloy after remelting and casting. This verifies that the improvement of mechanical properties of such kind of material possesses stability and reliability.  相似文献   

16.
《Materials Letters》2005,59(24-25):3014-3017
Ni–SiC metal matrix composites with two kinds of SiC content were prepared by electroforming in a nickel sulphamate bath. Tensile strength and microstructure of the composites before and after heat treatment were investigated. The maximum of tensile strength was obtained after heat treatment at 300 °C × 24 h. The values were 641 N/mm2 and 701 N/mm2 respectively. The complete reaction between nickel and SiC particles can produce shrinkage pores in the interface. The volume of shrinkage pores was equal to 8% of the volume of SiC particles in the composites. The interfacial reaction products were composed of Ni3Si and a little amount of Ni31Si12 after heat treatment at 600 °C × 24 h. The fracture evolution went though microcracks initiation, growth and coalescence. Cracking of the matrix, debonding of Ni–SiC interfaces and cracking of particles were three types of cracking modes for Ni–SiC composites.  相似文献   

17.
A metal matrix composite has been obtained by a novel synthesis route, reacting Al3Ti and graphite at 1000 °C for about 1 min after ball-milling and compaction. The resulting composite is made of an aluminium matrix reinforced by nanometer sized TiC particles (average diameter 70 nm). The average TiC/Al ratio is 34.6 wt.% (22.3 vol.%). The microstructure consists of an intimate mixture of two domains, an unreinforced domain made of the Al solid solution with a low TiC reinforcement content, and a reinforced domain. This composite exhibits uncommon mechanical properties with regard to previous micrometer sized Al–TiC composites and to its high reinforcement volume fraction, with a Young’s modulus of ∼110 GPa, an ultimate tensile strength of about 500 MPa and a maximum elongation of 6%.  相似文献   

18.
Rapidly increasing packaging density of electronic devices puts forward higher requirements for thermal conductivity of glass fibers reinforced polymer (GFRP) composites, which are commonly used as substrates in printed circuit board. Interface between fillers and polymer matrix has long been playing an important role in affecting thermal conductivity. In this paper, the effect of interfacial state on the thermal conductivity of functionalized Al2O3 filled GFRP composites was evaluated. The results indicated that amino groups-Al2O3 was demonstrated to be effective filler to fabricate thermally conductive GFPR composite (1.07 W/m K), compared with epoxy group and graphene oxide functionalized Al2O3. It was determined that the strong adhesion at the interface and homogeneous dispersion of filler particles were the key factors. Moreover, the effect of interfacial state on dielectric and thermomechanical properties of GFRP composites was also discussed. This research provides an efficient way to develop high-performance GFRP composites with high thermal conductivity for integrated circuit packaging applications.  相似文献   

19.
In this research, microstructure and mechanical properties of 5052Al/Al2O3 surface composite fabricated by friction stir processing (FSP) and effect of different FSP pass on these properties were investigated. Two series of samples with and without powder were friction stir processed by one to four passes. Tensile test was used to evaluate mechanical properties of the composites and FSP zones. Also, microstructural observations were carried out using optical and scanning electron microscopes. Results showed that grain size of the stir zone decreased with increasing of FSP pass and the composite fabricated by four passes had submicron mean grain size. Also, increase in the FSP pass caused uniform distribution of Al2O3 particles in the matrix and fabrication of nano-composite after four passes with mean cluster size of 70 nm. Tensile test results indicated that tensile and yield strengths were higher and elongation was lower for composites fabricated by three and four passes in comparison to the friction stir processed materials produced without powder in the similar conditions and all FSP samples had higher elongation than base metal. In the best conditions, tensile strength and elongation of base material improved to 118% and 165% in composite fabricated by four passes respectively.  相似文献   

20.
《Composites Part A》2007,38(2):615-620
Al2O3–FeCrAl composites were fabricated by mixing Fe2O3, Al and Cr powders and then reactive hot pressing. The high temperature alloy FeCrAl was formed by the reaction of extra Al, Cr and the Fe reduced from Fe2O3. The Al2O3–FeCrAl composites with various Al2O3 fractions were successfully fabricated by the proper addition of extra Fe, Cr, Al or Al2O3 powders. A five-layer functionally graded material of YSZ–FeCrAl was fabricated using the Al2O3–FeCrAl composites with compositions of 25, 53.2 and 75 vol.% Al2O3 as interlayer. The results from XRD analysis, optical microscope observation and thermal cycling test show that the composites fabricated by this method consist of α-Al2O3 phase and (Fe, Cr, Al) solid solution. The α-Al2O3 grain formed by this in-situ reaction between Fe2O3 and Fe is ultrafine and uniform distribution. The three-point bending strength is 305.0 MPa for the composite with 53.2 vol.% Al2O3 prepared by the reactive hot pressing, about 20% higher than that of the composite with same composition prepared by ex situ hot pressing method (252.0 MPa). No cracking was found in the functionally graded materials after 10 thermal cycles up to 1000 °C due to the better metal–ceramic bond, continuous in microstructure at interface of FGM and good oxidation resistance component FeCrAl alloy formed in the FGM.  相似文献   

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