In-situ synthesis and mechanical properties of Zr-based bulk metallic glass matrix composites manipulated by nitrogen additions

Our study investigates in-situ synthesis and mechanical properties of Zr-based bulk metallic glass (BMG) matrix composites via arc plasma-induced accelerated displacement reaction (APADR) process. The aluminum nitride precursor under arc plasma-induced ultra-high temperature results in higher contents of dissolved nitrogen as well as precipitation of zirconium nitride (ZrN) particles in a Zr-based amorphous matrix. The nitrogen in the matrix results in a decrease of crystallization resistance (lower T_x and reduced glass-forming ability), but an increase of mechanical stability (a decrease of strain burst sizes). In particular, in-situ formed ZrN, which exhibits a homogeneous distribution and strong interfacial bonding with the matrix, causes an increase in compressive fracture strength and significant plastic deformation in the composite compared with the monolithic BMG. The formation of multiple shear bands and the enhancement of shear band interactions by the dissolved nitrogen as well as the in-situ formed ZrN particles were carefully confirmed by a statistical analysis on serrated flows. These results give us a guideline on how to manipulate nitrogen contents and fabricate in-situ BMG matrix composites with improved mechanical properties via APADR process.     

添加NH_4AlO（OH）HCO_3原位生成Al_2O_3/Al复合材料的制备及其性能

碳酸铝铵与熔融的铝液反应原位生成颗粒增强铝基复合材料,对复合材料的力学性能和摩擦磨损行为进行研究。结果表明：在搅拌的铝熔体中碳酸铝铵发生分解反应生成γ-Al2O3;该原位反应的增强颗粒比直接添加的Al2O3在铝熔体中分布得更均匀;复合材料的密度和硬度随着增强相加入量的增加而提高,而强度则随着增强相加入量的增加而降低;磨损率随着增强相加入量的增加和载荷的增加而提高;原位反应生成的复合材料的力学性能和耐磨性明显优于直接添加Al2O3颗粒形成的复合材料的。     

Production and mechanical properties (strength, wear, and fracture toughness) of chilled aluminum-quartz castable particulate composite

Structural composite materials offer an excellent opportunity to produce components that achieve weight savings and improved mechanical properties. This paper describes a chilled Al-quartz particulate composite that can be cast using metallic and nonmetallic chill blocks, much like nonreinforced aluminum, using conventional aluminum casting equipments. Unlike other metal matrix composites (MMCs), this material is produced economically by a simple ingot metallurgical process. An overview of the production process is given along with the techniques used for fabricating the chilled composite. The material’s mechanical properties, particularly its strength, wear resistance, fracture toughness, and hardness, are discussed in some detail. These properties offer attractive design opportunities for a variety of automotive, aerospace, and structural applications. The composite developed is shown to provide significant weight savings over ferrous metals. The present investigation aims at producing cast aluminum alloy-quartz particulate composites in molds, containing metallic and non metallic chill blocks, by dispersing quartz particles in molten aluminum alloy, above the liquidus temperature, the size of the particles dispersed being between 60 and 100 μm. The dispersoid being added ranges from 3 to 9 wt.% in steps of 3%. The resulting composites cast using chill blocks were tested for thier mechanical properties.     

碳化硅颗粒增强Al基复合材料的新型制备工艺

综述了碳化硅增强铝基复合材料的几种主要制备工艺,重点阐述了高能超声半固态复合法制备SiCp／Al复合材料。首先用渗流法制备SiC体积分数高的SiCp／Al预制块,进行SiC预分散,然后将预制块加入处于半固态温度条件下的铝合金熔体中,最后导入超声波进行搅拌。此法很好地改善了增强颗粒与基体之间的润湿性,使SiC在基体中均匀分布。     

Combination of reinforcing powders and matrix alloys for fabrication of aluminum matrix composites by plasma synthesis method

Several kinds of powders and aluminum alloys are adopted to study the feasibility of the fabrication of aluminum matrix composites through plasma synthesis. Some powders do not incorporate into the molten aluminum due to reflection on the melt surface and dissolution in the plasma arc. On the contrary, iron powders are well incorporated into the molten aluminum. The iron powders incorporated into the molten aluminum make angular Al₁₃Fe₄ intermetallic compounds in the matrix. In addition, some portion of iron powders dissolve into the matrix and change the microstructures of the matrix alloys. The effects of dissolved Fe on the microstructures and mechanical properties of the composites are examined.     

Mechanical properties of aluminum-based nanocomposite reinforced with fullerenes

The strengthening effect of fullerenes in aluminum matrix composites was investigated. The composites are produced using a two-step ball-milling technique combined with a hot rolling process. First, fullerene aggregates, where fullerene molecules initially come together to form giant particles (～200 μm in diameter) via van der Waals bonding, are shattered into smaller particles (～1 μm in diameter) by planetary milling. Second, primarily ball-milled fullerenes are dispersed in aluminum powder via attrition milling. Finally, aluminum/fullerene composite powder is consolidated by hot-rolling at 480 °C. For the composite sheet, grain refinement strengthening and dispersion hardening by fullerenes are accomplished at the same time, thereby exhibiting HV ～222 of Vickers hardness (e.g., ～740 MPa of yield strength) with only 2% (volume fraction) of fullerenes.     

Metallic coating of aerospace carbon/epoxy composites by the pulsed gas dynamic spraying process

A method for applying metallic coatings to high fibre volume fraction aerospace carbon/epoxy polymer matrix composites is presented. The pulsed gas dynamic spraying process was used for depositing zinc coatings on composites featuring a thin layer of copper particles co-cured into the laminate. No surface preparation was required on the cured substrates prior to spraying hence no damage was induced in brittle carbon fibres. Polymer matrix composite substrates with an added layer of co-cured copper particles were manufactured using a standard autoclave process. External substrate heating was not required. Metal powder and epoxy degradation were avoided through low process temperatures. Satisfactory cohesive and adhesive characteristics, low porosities and good microhardness values were obtained for a range of coating parameters. Microhardness and porosity of coatings deposited on polymer matrix composites compared well with those of similar coatings deposited on metallic substrates.     

颗粒增强铝基复合材料的半固态组织与性能

采用自制的半固态流变性能测试装置，研究了SiC颗粒增强铝基复合材料的半固态流变性能，并对其微观组织进行了分析。结果表明，在SiC颗粒体积分数低于12％的条件下，SiC颗粒越多，材料的半固态流变性能越好。半固态微观组织分析表明，SiC颗粒的分布状况与复合材料的半固态的变形量有关。     

Production of High-Strength Al/Al2O3/WC Composite by Accumulative Roll Bonding

In this study, Al/Al₂O₃/WC composites were fabricated via the accumulative roll bonding (ARB) process. Furthermore, the microstructure evolution, mechanical properties, and deformation texture of the composite samples were reported. The results illustrated that when the number of cycles was increased, the distribution of particles in the aluminum matrix improved, and the particles became finer. The microstructure of the fabricated composites after eight cycles of the ARB process showed an excellent distribution of reinforcement particles in the aluminum matrix. Elongated ultrafine grains were formed in the ARB-processed specimens of the Al/Al₂O₃/WC composite. It was observed that as the strain increased with the number of cycles, the tensile strength, microhardness, and elongation of produced composites increased as well. The results indicated that after ARB process, the overall texture intensity increases and a different-strong texture develops. The main textural component is the Rotated Cube component.     

废弃玻璃／铝基复合材料的组织和性能

利用搅拌熔铸法将废弃玻璃颗粒加入到熔融的基体合金ZL105中,制备出了废弃玻璃／铝基复合材料,研究了复合材料的微观组织,力学性能及断裂机理,结果表明,玻璃颗粒较均匀地分布于基体中,与基体发生界面反应;与基体合金相比,废弃玻璃颗粒的加入提高了复合材料的硬度和抗拉强度,在低载荷下,复合材料的摩擦性能优于基体合金,由于玻璃颗粒形状较尖锐,尺寸大小不均,并存在加工缺陷,有碍于大幅度提高复合材料的性能。     

高能超声场下熔体原位反应制备TiB2/Al-30Si复合材料及其耐磨性能

在高能超声场下利用熔体原位反应制备TiB2/Al-30Si复合材料;利用XRD、SEM及干磨损试验研究此复合材料的显微组织和磨损性能。结果表明：在高能超声场作用下,原位TiB2颗粒在铝基体中分布均匀,形貌为圆形或四边形,尺寸在0.1-1.5μm之间。初生硅的形貌为四边形,平均尺寸为10μm。随着高能超声功率的增加,Al-30Si基体合金及TiB2/Al-30Si复合材料的硬度明显提高;特别是当超声功率为1.2 kW时,复合材料的硬度达到412 MPa,是基体合金的1.3倍。复合材料的磨损性能得到明显提高,载荷的变化对复合材料的磨损量影响不大。     

Ni—Al三维网络（骨架）增强Al合金复合材料的磨损行为

提出了三维网络（骨架）增强金属基复合材料的新构思，设计和制备了一种新型的Ｎｉ－Ａｌ金属间化合物三维网络（骨架）增强Ａｌ合金复合材料，研究了其在干滑动摩擦条件下的磨损行为。结果表明，复合材料的抗磨损性能明显 地基体铝合金。共磨损行为主要为粘着磨损。     

The Effect of Plasma Spraying on the Microstructure and Aging Kinetics of the Al-Si Matrix Alloy and Al-Si/SiC Composites

The Al-Si (LM 13)-based matrix alloy reinforced with SiC particles containing 10, 20, and 30 vol.% SiC particles were spray-formed onto Al-Si substrates. The sprayed samples were directly subjected to a standard aging treatment (T551). From the experiments, it was observed that the high rate of solidification resulted in very fine silicon particles which were observed as continuous islands in the matrix and each island exhibited several very fine silicon crystals. Analysis showed that plasma-spraying caused an increased solid solubility of the silicon in the aluminum matrix. DSC measurements in the permanent mold-cast Al-Si matrix alloy and plasma-sprayed Al-Si matrix alloy showed that plasma-spraying causes an increase in the amount of GP-zone formation owing to the very high rate solidification after plasma-spraying. In the plasma-sprayed Al-Si/SiC composites GP zones were suppressed, since particle-matrix interfaces act as a sink for vacancies during quenching from high plasma process temperature. Introduction of SiC particles to the Al-Si age-hardenable alloy resulted in a decrease in the time required to reach plateau matrix hardness owing to acceleration of aging kinetics by ceramic SiC particles.     

Interactions of particles with solidifying front in Al_2O_(3P) /Al Si composites

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粒度组成对高体积分数SiC_p/Al复合材料性能的影响

采用凝胶注模法制备SiC预制件用于无压熔渗液态铝合金实现60～67 vol%SiCp/Al复合材料的近净成形制备,研究了碳化硅颗粒级配及热处理对复合材料力学和热学性能的影响.结果表明:不同粒度的SiC粉体在铝基体中分布均匀,无明显偏聚现象;采用较细的SiC颗粒级配和退火处理都能有效提高复合材料强度;粗颗粒级配能增大SiC在复合材料中的体积分数,有利于导热性能的提高和热膨胀系数的降低;SiCp/Al复合材料抗弯强度介于240～365 MPa,室温时热导率介于122～175 W·m-1·℃-1.之间,室温至250℃的平均线热膨胀系数小于7.5×10-6℃-1,满足电子封装的性能要求.     

Aluminum matrix composites reinforced by in situ Al2O3 and Al3Zr particles fabricated via magnetochemistry reaction

Aluminum matrix composites reinforced by in situ Al₂O₃ and Al₃Zr particles are fabricated from A356-Zr(CO₃)₂ system via magnetochemistry reaction, and the morphologies, sizes and distributions of the in situ particles as well as the microstructures, mechanical mechanisms of the composites are investigated by XRD, SEM, TEM and in situ tensile tests. The results indicate that with the pulsed magnetic field assistance, the morphologies of the in situ particles are mainly with ball-shape, the sizes are in nanometer scale and the distributions in the matrix are uniform. The interfaces between the in situ particles and the aluminum matrix are net and no interfacial outgrowth is observed. These are due to the strong vibration induced by the applied magnetic field in the aluminum melt, which in turn, accelerates the melt reactions. The effects of the magnetic field on the above contributions are discussed in detail.     

Effects of particle size,bimodality and heat treatment on mechanical properties of pumice reinforced aluminum syntactic foams produced by cold chamber die casting

In recent years,metal matrix syntactic foams (MMSFs) have become highly attractive owing to their unique physical,microstructural and mechanical features.Due to their promising potential for different industrial areas like automotive,aviation,and defense,these advanced engineering materials can also be evaluated as serious alternatives to particle reinforced metallic composites and conventional metallic foams.Differently from previously reported laboratory scaled techniques in the literature,this experimental effort focuses on the feasibility of MMSF manufacturing via a fully automated and industrial-based cold chamber die casting technique.Accordingly,1–2 mm,2–4 mm,and bimodal (50vol.%) natural-based pumice filled aluminum syntactic foams were manufactured utilizing a purpose-made casting machine.Physical,macroscopic,and microscopic examinations show that all of the fabricated samples display perfect matrix/filler harmony.Average density levels of fabricated syntactic foams range between 1.50 and 1.80 g·cm^-3 depending upon the pumice particles size interval.To assess mechanical responses,quasi-static compression tests were performed.Furthermore,half of the foam samples were subjected to heat treatment to explore possible influences of aging on the compressive features and damage modes.Results indicate that although the heat treatment enhances the compressive strength,plateau stress,and energy absorption properties of the fabricated foams,it changes damage mode of the samples by causing brittle dominant deformation.     

Microstructural Characterization and Tensile Behavior of Rutile(TiO_2)-Reinforced AA6063 Aluminum Matrix Composites Prepared by Friction Stir Processing

Rutile(TiO_2) particle-reinforced aluminum matrix composites were prepared by friction stir processing. The microstructure was studied using conventional and advanced characterization techniques. TiO_2 particles were found to be dispersed uniformly in the composite. Clusters of TiO_2 particles were observed at a higher particle content of 18 vol%. The interface between the TiO_2 particle and the aluminum matrix was characterized by the absence of pores and reactive layer.Sub-grain boundaries, ultra-fine grains and dislocation density were observed in the composites. TiO_2 particles improved the mechanical properties of the composites. However, a drop in tensile strength was observed at a higher particle content due to cluster formation. All the prepared composites exhibited ductile mode of fracture.     

Microstructure and thermal expansion of Ti coated diamond/A1 composites

A titanium coating fabricated via vacuum vapor deposition for diamond/Al composites was used to improve the interfacial bonding strength between diamond particles and Al matrix, and the Ti coated diamond particles reinforced Al matrix composites were prepared by gas pressure infiltration for electronic packaging. The surface structure of the Ti coated diamond particles was investigated by XRD and SEM. The interfacial characteristics and fracture surfaces were observed by SEM and EDS. The coefficient of thermal expansion(CTE) of 50% (volume fraction) Ti coated diamond particles reinforced Al matrix composites was measured. The Ti coating on diamond before infiltration consists of inner TiC layer and outer TiO₂ layer, and the inner TiC layer is very stable and cannot be removed during infiltration process. Fractographs of the composites illustrate that aluminum matrix fracture is the dominant fracture mechanism, and the stepped breakage of a diamond particle indicates strong interfacial bonding between the Ti coated diamond particles and the Al matrix. The measured low CTEs (5.07×10⁻⁶−9.27×10⁻⁶K⁻¹) of the composites also show the strong interfacial bonding between the Ti coated diamond particles and the Al matrix.     

Effect of Particle Size on the Microstructures and Mechanical Properties of SiC-Reinforced Pure Aluminum Composites

This article examined the effects of particle size and extrusion on the microstructures and mechanical properties of SiC particle-reinforced pure aluminum composites produced by powder metallurgy method. It has been shown that both particle size and extrusion have important effects on the microstructures and mechanical properties of the composites. The SiC particles distribute more uniformly when the ratio of the matrix powder size and SiC particle size approaches unity, and the smaller-sized SiC particles tend to cluster easily. The voids are found to coexist with the clustered and large-sized SiC particles, and they significantly decrease the density and mechanical properties of the composites. Extrusion can redistribute the SiC particles in the matrix and decrease the number of pores, thus make the SiC particles distribute more uniformly in the matrix, and enhance the interfacial bonding strength. The decrease in the SiC particle size improves the tensile strength and yield strength, but decreases the ductility of the composites.