Zhongliang Shi

Joining characteristics of oxidized SiC particles reinforced Al-Mg matrix composite prepared by reaction infiltration processing

The joining characteristics of oxidized SiC particles with Al–Mg alloy during reaction infiltration processing for fabrication of the composite were studied. From the measurement of weight changes due to the transformation from SiC into SiO2, it became clear that the thickness of SiO2 layer which was formed at the surface of SiC particles increased parabolically with holding time at the given exposing temperatures. The degree of oxidation of the preform made by SiC particles can be controlled by the application of the present oxidation data. The microstructure observed by field emission scanning electron microscopy showed network skeleton via necklike oxidized-joining among the SiC particles and the compressive strength of the perform increased with oxidation temperature. Furthermore, the microstructure of the composite which was fabricated by Al–2 wt% Mg alloy via reaction infiltration processing was examined and the formation of spinel was observed to join the matrix with the particles like a bridge, which is suitable to make the complicate and strong preforms for the near net-shape composites application in electronic packaging.

The effect of Si upon the interfacial reaction characteristics in SiCp/Al-Si system composites during multiple-remelting

The composite interfaces play an important role in determining the resultant composite properties, especially the development of interfacial reaction during remelting is critical to the commercialization and sustainable-development of metal matrix composites. In this paper, the interfacial reaction characteristics of SiCp/Al-Si system composites during multiple-remelting were investigated by Differential Scanning Calorimeter (DSC). It was found that the interfacial reactions were not sensitive to remelting number, remelting temperature and reinforcement volume fraction after a degree of reaction, and the results also suggested that the preventation effects of Si upon the interfacial reaction SiCp/Al were mainly attributed to the Si released from the interfacial reaction, while the original Si content in the master alloy also has the same effect only after a given Si content.

The oxidation of SiC particles and its interfacial characteristics in Al-matrix composite

The passive oxidation behavior of SiC particles has been studied in an electric furnace at atmospheric pressure and in dry air, the weight change due to the transformation from SiC into SiO2 is descibed as a function of exposed temperature and holding time. According to the oxidation data of SiC particles, the oxidation parameters and the degree of oxidation for SiC particles can be controlled. Controllable preoxidation of SiC particles is one of the keys for designing interface and interphase to achieve high performance aluminum composite. Consequently, the evolution of interfacial reaction products in 2014 aluminum alloy composite reinforced with oxidized-SiC particles after extended thermal exposure at elevated temperatures were further characterized by Scanning Electron Microscopy (SEM), Transmission Electron Microscopy (TEM), and X-ray diffraction. While it could act to prevent the interfacial reaction between SiC particles and aluminum alloy, the preoxidation of SiC particles led to the formation of other interfacial reaction products. The observation of the microstructure revealed that at elevated temperatures nano-MgO formed initially on the surface of the oxidized SiC particles and then turned into nano-MgAl2O4 crystal due to the reaction between the SiO2 and aluminum alloy containing Mg. TEM observations indicated that the oxidized layer on SiC particles was uniform and had a good bonding with SiC and aluminum alloy.

The passive-oxidized behavior of SiC particles and their jointing characteristics

Abstract The passive-oxidized behavior of as-received α-SiC particles has been studied on the basis of the weight changes of the transformation from SiC into SiO 2 , which are dependent on the elevated temperatures and time, the volume fraction of SiO 2 and its thickness by assuming a spherical dependence on the elevated temperatures and time that also shows the same parabolic trends as the curves of the weight gain. According to the oxidation data of SiC particles, the oxidation parameters for SiC particles and the oxidation degree of the preform made from as-received SiC particles can be selected. An oxidized-jointing network skeleton among the particles of the preform is formed, as observed by SEM. These oxidation characteristics of SiC particles are beneficial for producing complicate and strong preforms for composites application in electronic packaging and in the aerospace industry.

Interfacial reaction between the oxidized SiC particles and Al-Mg alloys

The interfacial reactions of oxidized SiC particles reinforced Al-Mg matrix composites were investigated by the field emission-scanning electron microscopy (FE-SEM), TEM and X-ray diffraction. It was found that the nanoscale MgO forms initially due to the interfacial reaction, then whether it reacts with molten Al continuously or not depends on the content of Mg in the matrix and its covering densification at the surface of particles. When there is not enough Mg in the matrix for the formation of dense MgO layer, MgO will transform into MgAl2O4 crystal owing to the continuous reaction with SiO2 and molten Al. When dense MgO layer forms at the surface of the particles due to the affluence of Mg for the initial reaction, it will protect the inner SiC from the attack of molten Al. However, the reaction products of both MgO and MgAl2O4 are thermo-stable phases at the surface of the particles under high temperature. The results clarify the interfacial reaction route and they are of great value to the control of the interfacial reactions and their interfacial design of the composites.

The melt structures above the liquidus in SiCp/Al composite

The properties and the structures of liquid melt above the liquidus play an important role in determining the resultant properties of the alloy and the composite. In this paper, the melt structures of SiCp/Al composites with two different reinforcement volume fractions were investigated using liquid metal X-ray diffraction and differential scanning calorimetry. The experimental results showed that the melt structures of SiCp/Al composite are different from that of liquid matrix alloy, a Si–Si hump in the pair radial distribution function in SiCp/Al composite melt and the DSC trace indicated that Si is not well distributed above the liquidus, the size change of short-range-order (SRO) in SiCp/Al composite melt indicated the diffusion of Si from chemical reaction between SiC and molten Al is possible only after a given temperature or after some extent concentration fluctuation of Si. The mechanisms for the observed phenomenon are also discussed in this paper.

A new process for the fabrication of in-situ particle reinforced metalmatrix composites

Abstract The fabrication processes of metal matrix composites are very important for their application. There are many kinds of processes used, such as the squeeze casting process, the vacuum-high pressure infiltration process and the stirring casting process. In this article a new brief process for the fabrication of particle reinforced metal matrix composites will be introduced that has been used for silicon particulate reinforced Al-based composite and zinc-based composite. This process is the rheological compocasting process of a multicomponent system, in which a part of the raw materials mix with the rest where the latter are in the form of semi-solid moltens. The primary phases that are in the semi-solid molten material are left and are used as reinforcement phases. The tests show that the process is feasible, convenient and practical.