Interface Behavior of Brazing between Zr-Cu Filler Metal and SiC Ceramic

The interface behavior of brazing between Zr-Cu filler metal and SiC ceramic was investigated. Based on the brazing experiment, the formation of brazing interface products was analyzed using OM, SEM, XRD and other methods. The stable chemical potential phase diagram was established to analyze the possible diffusion path of interface elements, and then the growth behavior of the interface reaction layer was studied by establishing relevant models. The results show that the interface reaction between the active element Zr and SiC ceramic is the main reason in the brazing process the interface products are mainly ZrC and Zr2Si and the possible diffusion path of elements in the product formation process is explained. The kinetic equation of interfacial reaction layer growth is established, and the diffusion constant (2.1479 μm·s1/2) and activation energy (42.65 kJ·mol−1) are obtained. The growth kinetics equation of interfacial reaction layer thickness with holding time at different brazing temperatures is obtained.

Interfacial behaviors of p-type CeyFexCo4–xSb12/Nb thermoelectric joints

Interfacial diffusions and/or chemical reactions are one of the key issues for the reliability of CoSb3-based skutterudite thermoelectric (TE) joint, especially for the [Formula: see text]-type joint, which limits the applications of TE devices. We investigate the interfacial evolution for [Formula: see text]-type CeyFexCo[Formula: see text]Sb[Formula: see text]/Nb joints ([Formula: see text]–1, [Formula: see text], 3, 4) and combine the previous study on [Formula: see text]-type Yb[Formula: see text]Co4Sb[Formula: see text]/Nb joint to demonstrate the effect of TE materials on the interfacial microstructure and interfacial resistivity. The reaction–diffusion kinetic analysis shows that the TE materials has little effect on chemical reactions but strongly influence the Sb diffusions. The low energy barrier of Sb diffusion leads to the absent phase decomposition of skutterudites in CeyFexCo[Formula: see text]Sb[Formula: see text]/Nb joints. The interfacial resistivity of CeyFexCo[Formula: see text]Sb[Formula: see text]/Nb joints is related with Fe content and the interfacial reaction layer (IRL) growth. In addition, since the interfacial reaction layer growth rate and interfacial resistivity of CeyFexCo[Formula: see text]Sb[Formula: see text]/Nb joints are both low, Nb is an adequate barrier layer candidate material.

Interface Reaction between Ti3Al-based Alloy and Oxide Mold

Ti3Al based alloys are light and high-temperature materials, having potential wide applications in the aerospace and the aeronautical industries. Molten Ti is lively, and it is easy to react with the mold material during in the investment casting, and hence to form casting defects such as α contaminated layer in the metal near the surface and gas porosity, resulting in the deterioration of the surface quality and castings mechanical properties. Therefore, the mechanism of interfacial reaction between Ti3Al-based alloys and mold is necessary to study. In this paper, the interface reaction samples of Ti-24Al-15Nb-1Mo alloy and ZrO2(Y2O3stabilized) mold were prepared by actually investment casting. Optical microscopy, SEM, EMPA and micro-hardness tests were used to study the microstructures at metal side of interface, consider the element distribution and discuss the interfacial reaction mechanism. The results show that there is interface reaction between Ti-24Al-15Nb-1Mo alloy and ZrO2(Y2O3stabilized) mold, and it belongs to the typical bilateral diffusion reaction. The elements of Zr, Y, O diffuse into molten metal, at the same time, the matrix elements spread to the oxide mold, then form interfacial reaction layer. It has been found that the interfacial reaction was not uniform in the whole interface. In the thick-wall of castings, the interfacial reaction layer was thicker, and in thin-wall, the interfacial reaction layer was thinner.