通过调整润湿性开发具有高抗损伤性能的仿珍珠贝壳层状2024Al/B4C复合材料

为了解决复合材料中B4C陶瓷相难以被金属铝润湿的问题,利用TiH2和B4C的原位反应引入TiB2,进而调节其润湿性和界面结合.通过将熔融合金压力浸渗到冷冻铸造法制备的多孔陶瓷支架中,制备具有层状结构的2024Al/B4C?TiB2复合材料.与2024Al/B4C复合材料相比,加入TiH2后复合材料的抗弯强度和裂纹扩展韧...     

Mechanical properties and fracture of Al–15 vol.-%B4C based metal matrix composites

The present work was performed on three aluminium metal matrix composites (MMCs) containing 15 vol.-%B₄C particles. The matrix in two of these materials is pure aluminium, whereas the matrix of the third material was an experimental 6063 aluminium alloy. All composites were homogenised at elevated temperatures for 48 h before being quenched in warm water. The quenched samples were aged in the range of 25–400°C for 10 h, at each temperature. Hardness and tensile tests performed on the aged MMCs show that the presence of Zr (with or without Ti) resulted in a noticeable hardening due to the precipitation of a Zr rich phase. Maximum strengthening was obtained from the 6063 based MMC due to the precipitation of Mg₂Si phase particles. The present technique used to produce the MMCs examined proved capable of manufacturing composites with a uniform distribution of B₄C in the matrix with a strong degree of matrix/particle bonding. When the MMC samples were deformed to failure, the B₄C was fractured transgranularly without debonding from the matrix. The addition of Zr and Ti resulted in the formation of protective layers around the B₄C particles that were retained after fracture; these protective layers were not affected by the B₄C particle size (0·15–20 μm). Stacking faults were commonly observed in fractured Al 6063/B₄C/15p samples. The precipitation of zirconium–titanium compounds during aging contributed to the composite strength.     

In-Situ (TiB+TiC) particulate reinforced titanium matrix composites: Effect of B4C size and content

This study investigated the microstructure and tensile behavior of (TiB+TiC) reinforced titanium matrix composites (TMCs) using an in-situ reaction between Ti and B₄C. Different B4C sizes (1,500 and 150 μm) and contents (0.94, 1.88 and 3.76 mass%) were added to pure Ti to produce 5, 10, and 20 vol% (TiB+TiC) reinforced TMCs. In-situ synthesized TiB and TiC reinforcements prepared with 150 μm B₄C were very fine, and were distributed more homogeneously than the 1,500 μm B₄C. As the TiB and TiC contents increased, the tensile strength increased and the ductility decreased compared to unreinforced pure Ti. The improvements in the tensile strength of TMCs were obtained by load transfer strengthening and an alpha-Ti matrix grain reduction of 9–26%. In addition, the TMCs produced using 150 μm B₄C showed a greater tensile elongation of approximately 61–117%, with a slightly improved strength compared to that with 1,500 μm B₄C. The tensile elongation of TMCs obtained with 150 μm B₄C was enhanced because the coarse reinforcements produced by 1,500 μm B₄C were more easily and frequently cracked at the fracture surface.     

Effect of the B<Subscript>4</Subscript>C content on the structure and thermal expansion coefficient of the Al–5% Cu alloy-based metal-matrix composite material

The Al–5% Cu alloy-based metal-matrix composite materials reinforced with 5-μm B₄C particles have been produced using mechanical mixing-in method. A process of addition of the B₄C particles into the melt has been developed. A homogeneous distribution of the B₄C reinforcing particles in the metal-matrix composite matrix was obtained. Using X-ray diffraction analysis, the formation of Al₃BC and AlB₂ phases has been revealed at the interphase matrix/particle boundary, which indicates a good interaction in the phases. With increasing B₄C content in the matrix alloy, an insignificant increase in the porosity (from 1 to 3.1%) occurs. The average linear thermal-expansion coefficient is reduced from 24.5 to 22.6 × 10^–6 K^–1 in the temperature range of 20–100°C.     

Superior Tribological Properties of Particulate Aluminum Matrix Nano Composites

Aluminum is the best metal for producing metal matrix composites which are known as one of the most useful and high-tech composites in our world. Combining aluminum and nano Al₂O₃ particles will yield a material with high mechanical properties. Characterization of tribological properties revealed that the presence of nano particles significantly increased wear resistance of the composite. In case of unreinforced Al alloy, the depth of penetration is governed by the hardness of the specimen surface and applied load. But, in case of Al matrix composite, the depth of penetration of the harder asperities of hardened steel disk is primarily governed by the protruded hard ceramic reinforcement. The hard Al₂O₃ particles act as a protrusion over the matrix, carries a major portion of the applied load and protect the abrasives from penetration into the specimen surface.     

Production and characterization of a three-dimensional cellular metal-filled ceramic composite

Silicon carbide in the form of a foam network was vacuum infiltrated with aluminum alloy A356 to produce a new Interpenetrating Composite material. The foam, once infiltrated with a second phase transforms into a composite where two distinct, continuous, three-dimensional network structures are formed. The advantage of this metal matrix composite is its high strength-to-weight ratio for use in lightweight applications such as electronic packaging materials. The electroless nickel coating and vacuum infiltration procedures are developed. Materials characterization of the composite is evaluated by microstructural and compositional analysis, and density, porosity, and nano-indentation measurements. Selected experimental mechanical and thermal property measurements are performed to understand its properties and compare against theoretical models. Results show the final composite to have lower density than conventional electronic base plate packaging materials with low porosity. The composite has an increased Young's modulus and flexural strength to that of the unreinforced alloy and comparable impact toughness to composites with 50–70 vol% SiC particles but with only 12 vol% SiC. The fracture surface of the matrix illustrates conventional fibrous fracture and brittle cleavage whilst the reinforcement struts show signs of layer de-bonding from their SiC layered structure.     

Fabrication and characterization of cast magnesium matrix composites by vacuum stir casting process

A vacuum stir casting process is developed to produce SiC_p reinforced cast magnesium matrix composites. This process can eliminate the entrapment of external gas onto melt and oxidation of magnesium during stirring synthesis. Two composites with Mg-Al9Zn and Mg-Zn5Zr alloys as matrices and 15 vol.% SiC particles as reinforcement are obtained. The microstructure and mechanical properties of the composites and the unreinforced alloys in as-cast and heat treatment conditions are analyzed and evaluated. In 15 vol.% SiC_p reinforced Mg-Al9Zn alloy-based composite (Mg-Al9Zn/15SiC_p), SiC particles distribute homogenously in the matrix and are well bonded with magnesium. In 15 vol.% SiC_p reinforced Mg-Zn5Zr alloy-based composite (Mg-Zn5Zr/15SiC_p), some agglomerations of SiC particles can be seen in the microstructure. In the same stirring process conditions, SiC reinforcement is more easily wetted by magnesium in the Mg-Al9Zn melt than in the Mg-Zn5Zr melt. The significant improvement in yield strength and elastic modulus for two composites has been achieved, especially for the Mg-Al9Zn/15SiC_p composite in which yield strength and elastic modulus increase 112 and 33%, respectively, over the unreinforced alloy, and increase 24 and 21%, respectively, for the Mg-Zn5Zr/15SiC_p composite. The strain-hardening behaviors of the two composites and their matrix alloys were analyzed based on the microstructure characteristics of the materials.     

Manufacturing and recycling of A380Al/SiC(p) composites

The melting and degassing equipment and the process used in the production of particulate aluminum matrix composites is proposed. Also presented is the successful preparation of A380/80 μm SiC particulate aluminum alloy composites, where SiC particulate was evenly dispersed throughout an aluminum alloy matrix and a die cast chain wheel had very little porosity. In addition, recycling equipment for particulate aluminum matrix composites was designed. The old material and new material of these composites are mixed in ratios of 1:1, 2:1, and 3:1 by weight. After the first, second, and third recyclings, it was found that the amount of porosity and inclusion is much less for recycled composites. In addition, from composition analysis, it was found that the Si content increases with an increase in the amount of old materials and recycling times. From tensile strength tests, it was found that tensile strength and elongation are the same for new materials and composites with old material to new material weight ratios of 1:1 and 2:1 for the first to the third recyclings. However, tensile strength and elongation decrease for composites with an old material to new material weight ratio of 3:1 for the first to the third recyclings, in particular for material of the third recycling. If Si was added before the recycling process, though the formation of Al₃C₄ and Si crystal could be constrained, it would have no significant effect on the increase of elongation.     

Wear behavior of AI-Si alloy matrix composites reinforced by γ-Al2O3 decomposed from AACH

The Al-Si alloy matrix composite reinforced by γ-Al2O3 particles was produced by adding NH4AlO（OH）HCO3（AACH） into molten Al-Si alloy at 850℃. During stirring γ-Al2O3 particles are formed by the decomposing reaction of AACH. It is found that the γ-Al2O3 particles distribute more uniformly in the matrix by adding AACH than by adding γ-Al2O3 directly. The wear tests show that the volume loss of the unreinforced Al-Si alloy matrix is about 3 times larger than that of the γ-Al2O3 reinforced composites and that of the composites fabricated by adding γ-Al2O3 is larger than that by adding AACH.     

Comparison of wear behaviour of LM13 Al−Si alloy based composites reinforced with synthetic (B4C) and natural (ilmenite) ceramic particles

Dry sliding wear behaviour of stir-cast aluminium matrix composites (AMCs) containing LM13 alloy as matrix and ceramic particles as reinforcement was investigated. Two different ceramic particle reinforcements were used separately: synthetic ceramic particles (B₄C), and natural ceramic particles (ilmenite). Optical micrographs showed uniform dispersion of reinforced particles in the matrix material. Reinforced particles refined the grain size of eutectic silicon and changed its morphology to globular type. B₄C reinforced composites (BRCs) showed maximum improvement in hardness of AMCs. Ilmenite reinforced composites (IRCs) showed maximum reduction in coefficient of friction values due to strong matrix−reinforcement interfacial bonding caused by the formation of interfacial compounds. Dry sliding wear behaviour of composites was significantly improved as compared to base alloy. The low density and high hardness of B₄C particles resulted in high dislocation density around filler particles in BRCs. On the other hand, the low thermal conductivity of ilmenite particles resulted in early oxidation and formation of a tribo-layer on surface of IRCs. So, both types of reinforcements led to the improvement in wear properties of AMCs, though the mechanisms involved were very different. Thus, the low-cost ilmenite particles can be used as alternative fillers to the high-cost B₄C particles for processing of wear resistant composites.     

Ti 元素对B4C/Al复合材料力学性能的改善作用研究

B₄C/Al复合材料是目前最理想的中子吸收材料,广泛用于乏燃料储存。本文利用液态搅拌法制备B₄C/Al复合材料,通过添加Ti元素,探讨了界面反应对材料的界面结构和力学性能的影响。研究发现,Ti元素通过参与界面反应,改变了界面结构,在B₄C颗粒表面形成了紧密结合的纳米TiB₂界面层;Ti的添加消除了界面微裂纹、微孔、分离等缺陷。随着界面反应程度的加强,材料强度提高,尤其反应脱落的纳米TiB₂颗粒作为原位第二强化相进一步增强基体。B₄C/Al复合材料断裂过程表现为韧窝延性断裂;TiB₂界面层增强了B₄C颗粒与基体的结合,断裂行为从B₄C-Al界面脱落转变为B₄C颗粒断裂;但过渡的界面反应会形成微韧窝,引起材料延伸率下降。     

Nano-SiCP particles distribution and mechanical properties of Al-matrix composites prepared by stir casting and ultrasonic treatment

Nano-ceramic particles are generally difficult to add into molten metal because of poor wettability. Nano-SiC_Particles reinforced A356 aluminum alloy composites were prepared by a new complex process, i.e., a molten-metal process combined with high energy ball milling and ultrasonic vibration methods. The nano particles were β-SiC_P with an average diameter of 40 nm, and pre-oxidized at about 850 °C to form an oxide layer with a thickness of approximately 3 nm. The mm-sized composite granules containing nano-SiC_P were fi rstly produced by milling the mixture of oxidized nano-SiC_P and pure Al powders, and then were remelted in the matrix-metal melt with mechanical stirring and treated by ultrasonic vibration to prepare the composite. SEM analysis results show that the nano-SiC_P articles are distributed uniformly in the matrix and no serious agglomeration is observed. The tensile strength and elongation of the composite with 2 wt.% nano-SiC_P in as-cast state are 226 MPa and 5.5%, improved by 20% and 44%, respectively, compared with the A356 alloy.     

High Wear-Resistant Aluminum Matrix Composite Layer Fabricated by MIG Welding with Lateral B<Subscript>4</Subscript>C Powder Injection

In this work, a low-cost technique combining MIG welding and lateral powder injection was developed to fabricate B₄C particles-reinforced aluminum matrix composite (AMC) layer on a T6 heat-treated 7075 aluminum alloy (AA7075-T6) substrate. The AMC layer was 6-7 mm thick and well bonded to the substrate. The B₄C particles were dispersed throughout the AMC layer with an average content of approximately 7 vol.%. No significant reaction products existed either at the particle–matrix interface or in the Al-matrix. In pin-on-disk dry sliding wear tests against Al₂O₃ grinding wheels, the AMC layer exhibited excellent wear resistance with volume wear rate approximately 1/10-3/10 that of the quenched AISI 1045 steel and only approximately 2-7% that of the AA7075-T6 alloy under the same wear conditions. A small addition of ceramic particles can greatly improve wear resistance, suggesting that this technique has good prospects for a wide variety of applications.     

Microstructure and Strength of Al2O3 and Carbon Fiber Reinforced 2024 Aluminum Alloy Composites

The microstructure and mechanical properties of 2024 aluminum alloy composite materials strengthened with Al₂O₃ Saffil fibers or together with addition of carbon fibers were investigated. The fibers were stabilized in the preform with silica binder strengthened by further heat treatment. The preforms with 80-90% porosity were infiltrated by direct squeeze casting method. The microstructure of the as-cast specimens consisted mainly of α-dendrites with intermetallic compounds precipitated at their boundaries. The homogenization treatment of the composite materials substituted silica binder with a mixture of the Θ phase and silicon precipitates distributed in the remnants of SiO₂ amorphous phase. Outside of this area at the binder/matrix interface, fine MgO precipitates were also present. At surface of C fibers, a small amount of fine Al₃C₄ carbides were formed. During pressure infiltration of preforms containing carbon fibers under oxygen carrying atmosphere, C fibers can burn releasing gasses and causing cracks initiated by thermal stress. The examination of tensile and bending strength showed that reinforcing of aluminum matrix with 10-20% fibers improved investigated properties in the entire temperature range. The largest increase in relation to unreinforced alloy was observed for composite materials examined at the temperature of 300 °C. Substituting Al₂O₃ Saffil fibers with carbon fibers leads to better wear resistance at dry condition with no relevant effect on strength properties.     

Nanostructured Al-Based Metal Matrix Composite Coating Production by Pulsed Gas Dynamic Spraying Process

The advantage of combining cryomilling and pulsed gas dynamic spraying (PGDS) processes in order to produce a nanostructured, dense and wear resistant coating was demonstrated. Cryomilling was successfully employed to synthesize particulate B₄C reinforced Al matrix nanocomposite feedstock powders, while the PGDS process shows the ability of preserving the microstructure of the starting material. In this study, nanocrystalline and conventional Al5356?+?20%B₄C composite as well as the unreinforced Al5356 alloy feedstock powders were used. The influence of the nature of the feedstock material on the microstructure and mechanical properties of the coatings was studied. The PGDS process provides an opportunity to preserve the phase of the starting material, to produce hard and dense coatings with good cohesion between deformed particles and good adhesion to the substrate. High dry sliding wear resistance was observed when cryomilled composite material was used.     

Al_(0.25)Cu_(0.75)FeNiCo颗粒增强铝合金的组织与性能

高熵合金是一种新型的结构与功能材料,源于金属-金属间天然的界面结合特性,高熵合金与铝合金基体间的界面润湿性极好。采用Al_(0.25)Cu_(0.75)FeNiCo高熵合金(HEA)颗粒作为增强相来增强铝合金,研究高熵合金含量变化对复合材料显微组织和力学性能的影响。结果表明:高熵合金增强相在基体中分布均匀,随着高熵合金体积分数的增大,局部会出现少量颗粒团聚现象。复合材料的弹性模量和硬度随着高熵合金含量的增加而增大,但复合材料的抗拉强度和延伸率呈现出先增大后减小的趋势。当高熵合金的体积分数为5%时,复合材料的极限抗拉强度和伸长率达到最大值(σb:437.6 MPa,ε:11.42%),比铝合金基体分别提高了20.1%和36.6%。TEM分析表明,高熵合金颗粒和铝合金良好的界面结合状态,使得复合材料具有较高的综合力学性能。     

Processing,characterization, room temperature mechanical properties and fracture behavior of hot extruded multi-scale B4C reinforced 5083 aluminum alloy based composites

Microstructural characteristics and mechanical behavior of hot extruded Al5083/B₄C nanocomposites were studied. Al5083 and Al5083/B₄C powders were milled for 50 h under argon atmosphere in attrition mill with rotational speed of 400 r/min. For increasing the elongation, milled powders were mixed with 30% and 50% unmilled aluminum powder (mass fraction) with mean particle size of >100 μm and <100 μm and then consolidated by hot pressing and hot extrusion with 9:1 extrusion ratio. Hot extruded samples were studied by optical microscopy, scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), transmission electron microscopy (TEM), tensile and hardness tests. The results showed that mechanical milling process and presence of B₄C particles increase the yield strength of Al5083 alloy from 130 to 566 MPa but strongly decrease elongation (from 11.3% to 0.49%). Adding <100 μm unmilled particles enhanced the ductility and reduced tensile strength and hardness, but using the >100 μm unmilled particles reduced the tensile strength and ductility at the same time. By increasing the content of unmilled particles failure mechanism changed from brittle to ductile.     

Influence of addition of Grp/Al2O3p with SiCp on wear properties of aluminum alloy 6061-T6 hybrid composites via friction stir processing

Aluminum alloy base surface hybrid composites were fabricated by incorporating with mixture of (SiC+Gr) and (SiC+Al₂O₃) particles of 20 μm in average size on an aluminum alloy 6061-T6 plate using friction stir processing (FSP). Microstructures of both the surface hybrid composites revealed that SiC, Gr and Al₂O₃are uniformly dispersed in the nugget zone (NZ). It was observed that the addition of Gr particles rather than Al₂O₃ particles with SiC particles, decreases the microhardness but immensely increases the dry sliding wear resistance of aluminum alloy 6061-T6 surface hybrid composite. The observed microhardness and wear properties are correlated with microstructures and worn micrographs.     

Using ARB process as a solution for dilemma of Si and SiCp distribution in cast Al-Si/SiCp composites

A major challenge in achieving the best potential of SiC_p-reinforced aluminum composites is to homogeneously disperse SiC particles within the aluminum alloys. The presence of coarse Si fibers with non-uniform distribution in cast Al-Si alloys, which may lead to poor mechanical properties, is another important problem that limits the application of these alloys. In order to eliminate these problems, accumulative roll bonding (ARB) process was used in this study as a very effective method for improving the microstructure and mechanical properties of the Al356/SiC_p composite. It was found that when the number of ARB cycles was increased, the uniformity of the Si and SiC_p in the aluminum matrix improved, the Si particles became finer and more spheroidal, the free zones of Si and SiC particles disappeared, the porosity of composite decreased, the bonding quality between SiC_p and matrix improved, and therefore mechanical properties of the composites were improved. The microstructure of the manufactured Al356/SiC_p composite after six ARB cycles indicated a completely modified structure so that its tensile strength and elongation values reached 318 MPa and 5.9%, which were 3.1 and 3.7 times greater than those of the as-cast composite, respectively.     

Electrochemical corrosion behavior of Al–Si alloy composites reinforced with in situ TiB2 particulate

Understanding the corrosion behavior of TiB_2p‐reinforced aluminum matrix composites is crucial for their development as effective composites. In this work, corrosion characteristics of in situ TiB₂ particulate reinforced Al–Si alloy (A356) composite after T6 treatment are investigated by electrochemical techniques. The electrochemical impedance spectroscopy (EIS) reveals that the protection of nature film for the composites is worse than that for A356 alloy. Polarization experiments testify that the composites are susceptible to corrosion compared with their matrix alloys. Moreover, the corrosion resistance of the composites markedly decreases with increase in the TiB₂ content. The observations of the corrosion morphologies after polarization test show that the corrosion primarily occurs at the interdendritic sites with a large amount of TiB₂ particulates. Corrosion progress continues into the composite inner along the regions of α‐Al dendrite. The poor corrosion resistant properties of the composites are considered primarily due to the galvanic corrosion between noble TiB₂ reinforcements and more active aluminum matrix, as well as the weak protection of the defective nature film on the composite.