SiC-Al Interface Research Articles

Bifunctional nano-SiO2 additive for reinforcing the SiC/Al composites fabricated via a novel hybrid additive manufacturing

In this work, a novel hybrid additive manufacturing technique is used to prepare the SiC/Al composites. The effect of silica sol concentration on the microstructure and property of SiC preforms and SiC/Al composites were investigated. Silica sol infiltration proved to be an efficient strategy to address the troublesome issue of strength decrease for the SiC preforms after preoxidation. With an increase in silica sol concentration from 0 to 30 %, the strength of the pre-oxidised SiC preforms increased from 0 to 2.77 ± 0.21 MPa, which well satisfied the processing requirements of the subsequent vacuum-pressure infiltration process. Interestingly, the nano-SiO2 in the silica sol not only is favorable for the SiC–Al interface of SiC/Al composite, but also has a significant grain refinement effect on the aluminium matrix. As a result, the strength of the samples treated with preoxidation and silica sol infiltration reached a maximum value of 411.41 MPa, which was 88.38 % higher than 218.4 MPa of the control group. Meanwhile, a notable enhancement in fracture strain was observed from 0.125 to 0.156 % for the optimized SiC/Al composite. More importantly, the large-size and high-performance SiC/Al composite parts with complex structures have been successfully prepared by this hybrid additive manufacturing technique. The results of this work show that the hybrid additive manufacturing technology has great potential for application in aerospace, automotive industry and other fields.

Multiscale 3D finite element analysis of aluminum matrix composites with nanoµ hybrid inclusions

The present work proposed a multiscale finite element (FE) analytical approach to investigate the mechanical behavior of elasto-plastic aluminum matrix composites reinforced with nano-micro hybrid inclusions. To study the effect of microstructural effects, 3D representative volume elements (RVEs) of nano- and micro-scales are established, where the nano-RVE considers the aluminum matrix with carbon nanotubes (CNTs)-reinforcement whose homogenization is treated as the equivalent matrix (EM) phase for micro-RVE with SiC particles. The FE-based ABAQUS simulation is employed to recover the local stress distributions within RVE of either scales, and the corresponding effective stress–strain relationship, damage and failure behavior are calculated and predicted. Results generated from the present simulations are validated against the experimental measurement of CNTs/SiC/Al composites and good agreement is generally obtained. What’s more, several microstructural parameters are tested on the composites’ effective behavior, including the elaso-plastic constitutive relation and damage response of aluminum matrix, the elastic-brittle failure mechanical behavior of the micro-scale SiC particles. We also consider the traction-separation mechanical behavior at the SiC-Al interface. It is demonstrated that the present numerical method is suitable to study the comprehensive behavior of composites with hybrid inclusions.

An investigation on particle weakening in T6-treated SiC/Al–Zn–Mg–Cu composites

This study found weakening effect of SiC particles on strength of a T6-treated SiC/Al–Zn–Mg–Cu composite. The mechanisms for the weakening were investigated in detail for the first time. The 15 vol% SiC/7085Al composite and 7085Al alloy were fabricated by powder metallurgy (PM) method and subjected to microstructural examination and mechanical properties evaluation. It was indicated that the as-extruded composite had 92 MPa enhancement in the ultimate tensile strength (UTS) compared to the as-extruded unreinforced alloy. However, After T6 treatment (solution treatment and artificial ageing), the UTS of the composite was 34 MPa lower than that of the unreinforced alloy. Microstructural examination disclosed that the content of η′-MgZn2 was reduced in the T6-treated composite due to interface reaction between Mg and oxide on the surface of SiC particles. Meanwhile, compared to the unreinforced alloy, the composite had coarser precipitates with relative lower density under the T6 condition. Furthermore, it was found that SiC particles accelerated ageing process, leading to formation of coarse precipitates and precipitate free zone in the vicinity of SiC–Al interface. According to the theoretical calculation, the weakened precipitation strengthening value was not compensated by mismatch dislocation strengthening and load transfer strengthening. By adding additional Mg (1.0 wt%) into the composite, the precipitation strengthening effect could be basically recovered, resulting in significantly enhanced strength compared to the 7085Al alloy.

Effect of exfoliated few-layered graphene on corrosion and mechanical behaviour of the graphitized Al–SiC surface composite fabricated by FSP

The influence of friction stir processing parameters and the subsequent evolution of microstructures and corrosion behaviour of Al–SiC surface composites fabricated in the presence of graphitic flakes are presented in this paper. The circumferential shear stress exerted by the rotating tool exfoliates the graphite flakes into few-layered graphene during processing. These graphene flakes preferentially occupy both the grain boundaries and the SiC–Al interface during recrystallization. The potentiodynamic polarization test, in 3.5 wt% sodium chloride (NaCl) solution, is conducted for samples processed at various tool rotational speeds and it is found that the presence of this thin graphitic layer at these locations reduces the intergranular and interfacial corrosion to a great extent. The tool rotational speed has a significant influence on processing, and samples fabricated at an optimum tool rotational speed of 2200 rpm shows better corrosion resistance and mechanical properties as compared to that at lower and higher speeds. Raman spectroscopic analysis, X-ray diffraction studies and microhardness tests corroborate the experimental results and the proposed mechanisms.

Interfacial valence electron localization and the corrosion resistance of Al-SiC nanocomposite.

Microstructural inhomogeneity generally deteriorates the corrosion resistance of materials due to the galvanic effect and interfacial issues. However, the situation may change for nanostructured materials. This article reports our studies on the corrosion behavior of SiC nanoparticle-reinforced Al6061 matrix composite. It was observed that the corrosion resistance of Al6061 increased when SiC nanoparticles were added. Overall electron work function (EWF) of the Al-SiC nanocomposite increased, along with an increase in the corrosion potential. The electron localization function of the Al-SiC nanocomposite was calculated and the results revealed that valence electrons were localized in the region of SiC-Al interface, resulting in an increase in the overall work function and thus building a higher barrier to hinder electrons in the nano-composite to participate in corrosion reactions.

Experimental observation and numerical simulation of SiC3D/Al interpenetrating phase composite material subjected to a three-point bending load

The failure process and the underlying mechanism of crack initiation, crack propagation and eventual fracture of SiC3D/Al interpenetrating phase composite subjected to a static three-point bending load were investigated using in-situ SEM observation and two-dimensional microstructure-embedded numerical simulation. It was found that stress concentration originally occurred in the SiC ceramic phase near the bottom of the specimen, causing horizontal tensile forces and inducing a vertical microcrack inside the SiC phase near the SiC–Al interface. With increased load, more microcracks were gradually initiated in the SiC phase, and severe tearing plastic deformation and cracking of the Al phase occurred at the base of the specimen. Subsequently, the microcracks propagated and connected to form a primary crack. It was notable that at the final stage of the primary crack, cracking in the Al phase no longer occurred due to the sudden release of the internal energy in the composite material. Interestingly, the primary crack bridged over the Al phase then continued to propagate in the SiC material. Simulated results were consistent with observed behavior.

Formation of SiC-Al Interface in SiC Whisker Reinforced Al Composite

Crystallization behavior of melt aluminum on the surfaces of SiC whisker (SiCw) was analyzed based on the consideration to obtain the SiC-Al interfaces with the lowest energy in SiCw/Al composite. The interfacial structure was investigated to determine whether a specific orientation relationship exists between SiC and Al. Analysis results indicate that four kinds of orientation relationships possibly exist between SiC and Al when only the <110> crystal direction of the aluminum is considered as the firstly formed crystal direction along the concave joint line of <110> of the SiC whisker. Interfacial atom match bonding models were set up in theory and one kind of crystal orientation relationship has been proved by our previous experimental result.

Corrosion Initiation and Anodic-Cathodic Alternation of Localized Corrosion of SiC-Reinforced Aluminum Composites in NaCl Solution

Localized corrosion initiated on a 6092-T6 aluminum-based metal-matrix composite (MMC) reinforced with 20 vol.% SiC particles in an air-exposed 3.15 wt% NaCl solution. SEM indicated that corrosion initiated around SiC reinforcements. The polarization diagrams under illumination suggested that the SiC reinforcements were p-doped and that a semiconductor/electrolyte junction barrier existed. It was hypothesized that Al4C3 formed at the SiC-Al interface during the processing of the Al/SiC MMC. In the presence of water, the Al4C3 hydrolyzes and can induce crevices at the Al-SiC interfaces. Corrosion could thus initiate from these crevices. The scanning vibrating electrode technique revealed that the net currents over the localized corrosion region switched from anodic to cathodic, while the scanning ion-selective electrode technique revealed that the solution near the localized corrosion region switched from acidic to alkaline. The effects of solution pH on the local potential fluctuations of aluminum are believed to be related to this alternation.

Microstructural Characterization and Properties of SiC/Al Composites for Electronic Packaging Fabricated by Pressureless Infiltration

High volume fraction (63vol.%) SiCp/Al composite for electronic packaging fabricated by pressureless infiltration was characterized by microscopy, physical and mechanical tests. Microscopy observations and XRD analysis indicated that the composite appeared to be free of porosity and macroscopically homogeneous, SiC-Al interface was atomic bonding interface with low thermal resistivity and electrical resistivity, no interfacial reaction products was detected. Examination of the fracture surfaces of the composites revealed that the cracks passed through the SiC particles and Al matrix, no debonding of SiC-Al interface was observed. The fracture mode indicated that the bonding between SiC-Al was sufficient strong. The properties of the composite were noted for its ultrahigh thermal conductivity of 235W/m·K and specific modulus (79.9×105m), low coefficient of thermal expansion (7.2×10-6/K) and density of 2.99g/cm3. The advantages of the composite over traditional materials used as the electronic packages for aerospace applications were analyzed.

Failure Mechanisms of a SiC Particles/2024Al Composite under Dynamic Loading

Dynamic mechanical response of a 20 vol% silicon carbide particles (SiCp) reinforced 2024 Al composite prepared by powder metallurgy techniques were studied with a split Hopkinson bar. The fracture mechanisms and the deformation microstructure were examined with Scanning Electron Microscopy (SEM) and Transmission Electron Microscopy (TEM). The present results indicate that the composite has a strong SiC-Al interfacial bonding; failure of the material is mainly caused by fracture of SiC particles and tearing failure of the SiC-Al interface. This failure by interface tearing with adhesion of an aluminium layer on SiC particles on the fracture surfaces has not been reported in SiC particle-reinforced aluminium composites. High-resolution transmission electron microscopy studies showed that many of the SiC-Al interfaces have coincident site lattice structures, which are considered to make a significant contribution to the strong interfacial bonding.

Low-temperature interface reaction in aluminium-silicon carbide particulate composites produced by mechanical alloying

An experimental investigation has been carried out on the reaction that takes place between 3 and 20 μm SiC particles and the aluminium alloy 1050 matrix of composite materials prepared by a mechanical alloying process. The work is different from that undertaken by other researchers in that the SiC-Al interface reaction has been studied in the temperature range 853–933 K, i.e., with the matrix initially in the solid state. Differential thermal analysis, X-ray diffraction and scanning electron microscopy all show that the SiC-Al reaction initiates in the solid state at temperatures as low as 883 K. The reaction produces Al4C3 and Si, the latter entering into solid solution in the aluminium matrix. At temperatures exceeding 903 K, the reaction produces a liquid phase and at this stage the speed of the interface reaction increases significantly. The results are discussed in terms of Al-Si-C metastable equilibrium and the kinetics of the reaction.

SiC-Al interface structure in squeeze cast [formula omitted] composite

SiC whisker reinforced aluminum alloy (SiCw/Al) composites are attractive as structural materials because of their high specific modulus and strength and also high wear and thermal resistance. On the one hand, the high properties of the SiCw/Al composites are mainly because of the addition of the SiC whiskers which have high modulus, strength and thermal resistance, and also because of the difference of the microstructure of the matrix alloy as compared with unreinforced alloy; on the other hand, the SiC-Al interface plays a very important role in the properties of the SiCw/Al composite. In the case of SiC-Al composite there have been no direct measurements of the bond strength, but indirect data indicate that the bond strength is quite good. The purpose of this research was to analyze the nature of the SiC-Al interface in squeeze cast SiCw/Al composite in detail, and try to explain why the squeeze casting SiCw/Al composite has a high interface bonding strength.

SiC-Al interface crystallographic orientation relationship in a squeeze-cast SiCw/Al composite

A SiC-Al interface in a squeeze-cast SiCw/6061 Al composite was studied by means of scanning transmission electron microscopy and high-resolution electron microscopy. A crystallographic orientation relationship was found at the SiC-Al interface and was identified as (011̄) sic//(001) Al, [211] sic//[100] Al. Based on crystallography theory, the formation mechanism of the orientation relationship was analyzed in detail. A semicoherent atom matching model of the SiC-Al interface was developed that can explain why the squeeze-cast SiCw/6061 Al composite has a high interface bond strength.

SiC-Al interface bonding mechanism in a squeeze casting SiCw/Al composite

SiC-Al interface bonding mechanism in a squeeze casting SiCw/Al composite

コンポキャスティング法による粒子分散型アルミニウム合金基複合材料の製造および諸特性

An attempt to fabricate particle dispersed Al-4mass% Cu alloy composites was made by compocasting. The recovery of particles introduced in the molten metal is governed by the particle size, fraction solid of the metal and Mg concentration in the metal. Mg 0.5mass% is required in the metal to ensure homogeneous dispersion of SiC particles 40μm in size in the molten metal. A spinel product MgAl2O4 is observed at the Al2O3 particle-Al interface, but no reaction product is found at the SiC-Al interface. The wear loss of the composites decreases with increases in size and content of dispersed Al2O3 particles so significantly that 2017 alloy containing 2.5mass% of Al2O3 particles is equivalent to FC25 cast iron in wear loss. Rolling of Al2O3 particle dispersed 2017 alloy composites results in a decrease in tensile elongation with increases of size and content of particles. The strength of the alloy containing dispersed Al2O3 20μm in size from 0 to 7.5mass% decreases only slightly by rolling.

Interfacial reactions between SiC and aluminium during joining

Reactions between SiC and liquid aluminium were studied. Transmission electron microscopy (TEM) showed that aluminium carbide (Al4C3) phase was formed at the interface between pressureless sintered SiC and aluminium. In contrast, the Al4C3 phase was not detected at the reaction sintered SiC-Al interface. This difference in microstructures results in the change in bending strength of the joints. Mixtures of SiC and aluminium powders were heated to react in vacuum in the temperature range 973 to 1473 K and the reaction products were examined using X-ray powder diffraction. It was confirmed that Al4C3 and silicon were formed, and that the extent of reaction between SiC and aluminium was decreased by the addition of silicon into aluminium.