Tongxiang Fan

Fabrication of in situ Al2O3/Al composite via remelting

Abstract In the present work, in situ Al 2 O 3 /Al composite was produced via CuO/Al composite and subsequent remelting, and the chemical reaction evolution and the fractography were investigated by means of differential scanning calorimeter (DSC), X-ray diffraction (XRD), electron probe micro-analysis (EPMA) and scanning electron microscopy (SEM). The experimental results showed that Al 2 O 3 could be successfully formed in situ by the addition of CuO to aluminum. The results also suggested that the fracture mechanism changed from interfacial debonding in copper oxide/Al composite to particle cracking in Al 2 O 3 /Al composite, which was largely attributed to interfacial bonding increased between in situ Al 2 O 3 particle and Al. The Cu–O stability in the present processing was also discussed from the point view of thermodynamics.

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 elastic and geometrical properties of micro- and nano-structured hierarchical random irregular honeycombs

All the five independent elastic properties/constants of micro- and nano-structured hierarchical and self-similar random irregular honeycombs with different degrees of cell regularity are obtained by analysis and computer simulation in this paper. Cell wall bending, stretching, and transverse shearing are the main deformation mechanisms of hierarchical honeycombs. The strain gradient effects at the micro-meter scale, and the surface elasticity and initial stress effects at the nano-meter scale are incorporated into all the deformation mechanisms in the analysis and finite element simulations. The results show that the elastic properties of hierarchical random irregular honeycombs strongly depend on the thickness of the first-order cell walls if it is at the micro-meter scale, and that if the thickness of the first-order cell walls is at the nano-meter scale, the elastic properties of hierarchical random irregular honeycombs are not only size-dependent, but are also tunable and controllable over large ranges. In addition, the geometrical properties of nano-structured hierarchical random irregular honeycombs are also tunable and controllable.

Polytypism of SiC and interfacial structure in SiCp/Al composites

In the present work, the polytypism of SiC and the interfacial structure between SiC and Al were investigated using X-ray diffraction (XRD) and high resolution transmission electron microscopy (HREM). It was approved that 15R could be juxtaposed with 6H stacking sequences in the same SiC reinforcement and a structural transformation zone was also observed. The Al4C3 compound can nucleate on SiC at the SiC/Al interface with the growth orientation parallel to the C axis of SiC. Mechanisms for the observed phenomena were also discussed in detail.

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.

Ternary diffusion coefficients—Theoretical treatment and application to theIn-situ-reinforced TiB2/Al composite

In the present work, a new model is developed to predict ternary diffusion coefficients in liquid state based on hard sphere theory and the Miedema model, and the diffusion coefficients are theoretically determined starting from the quantities of the pure component. Using this model, the diffusion coefficient of Ti in the TiB2/Al composite is evaluated and the influence of alloying element additions on the diffusion coefficient of Ti is discussed. The results indicate that additions of Si can promote the diffusion of Ti. Meanwhile, other elements including Cu, Fe, Mg, V, Ni, La, and Zr can hinder the diffusion of Ti. It is furthermore concluded that not only the phase diagram but also considerations concerning the kinetics are required to produce the desirable phases.