Papers by Author: Xin Yang Wang

Abstract: Al2O3 ceramics and carbon steels were brazed using Cu-Ti active filler metal. The weld interface was characterized using scanning electron microscopy, energy spectrometer and X-ray diffraction instrument. Effects of brazing temperature on interface microstructures and the shear strength of the joint were investigated. The results show that the optimum brazing process is brazing temperature of 1323K, holding 30 min. The brazed joints with good microstructure morphology and higher interface shear strength can be obtained under the optimum brazing process. Interface bonding zone consists of three layers: reaction layer close to the ceramic, brazing alloy layer and diffusion layer close to the steel. And Cu3Ti3O, TiFe and TiFe2 are confirmed to form in the interface bonding zone. The shear strength of the joint reaches 99MPa.

Abstract: Brazing with active filler alloys containing some active elements, which promotes wetting of ceramics surfaces, is one of the most widely methods for joining ceramics to metals. The joints formed by brazing A12O3 to metal by using copper-titanium-nickel (Cu-Ti-Ni) as brazing filler were investigated. The metals/ceramics joints were produced at a vacuum level of 10-2-10-3 Pa at 1273K, using a constant holding time of 10 min. The surfaces were studied both morphologically and structurally using scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS) and X-ray diffraction analysis (XRD). In the brazing process, copper and titanium in the braze alloy form a series of reaction products. The formation of Ti3Cu3O and Ti2Ni at the interface is characteristic of these joints. The estimated free energies of formation of the Ti3Cu3O and Ti2Ni are -119kcal/mol and -245.92 kJ ~-263.78kJ/mol at 1200~1288K respectively. The highly negative values for the free energies of formation suggest that these compounds are thermodynamically stable.

Abstract: The Fe-Based Al2O3-TiC Ceramic Composite was fabricated by combining the methods of Self-propagating High-temperature Synthesis with casting. The microstructures of ceramic layer and interface were characterized via SEM, EDS and X-ray diffraction. The Results show that the microstructure of ceramic layer is dense, and the in-situ Al2O3 and TiC particles with size of 1-2 μm are distributed on the ferrite matrix. The hardness of compact ceramic layer reaches 48HRC, and it has graded distribution from ceramic layer to the ferrite matrix. The composite interface between ceramic and matrix is compact, and takes on flexuous. The composite material bonds in a metallographic manner, with high bonding strength.