The spreading behaviour of Cu, CuSi, CuMnNi, and TiCuNi ller metals with Ti6Al4V titanium alloy base metal has been studied under gas tungsten arc welding heating. Test results showed that the wet angle of CuMnNi ller metal was the smallest (15°) and that of Cu was the largest (30°). With spreading, the liquid ller metal solidi ed and crystallised simultaneously, and formed a spherical crown brazing seam. The wettability and spreadability of the liquid ller metal were related to oxide scale actions with arc heating. These actions included the 'cleaning action of the cathode' and lashing activation action of electrifying ions and electrons. Furthermore, the very high temperature of the activation spot zone partly melted the base metal surface and near surface metal, and a thin liquid lm was accordingly formed that created a strong heating activation. It was also discovered that there was a column solid -liquid incongruent compound g(MeTi 2 ) at the interface of ller metal and base metal (MezCu, CuzNi, CuzMn). This compound grew to form an interface with the centre of the brazing seam and was embedded in it. The particular crystallising and growing mode in the arc heating helped grow the column solid -liquid incongruent compound g(MeTi 2 ).MST/5668

Galvanised steel sheets have been joined using an arc brazing processing technique with Cu 97 Si 3 as the filler metal. Gas metal arc (GMA) brazing and gas tungsten arc (GTA) brazing tests were conducted in flowing argon and with varying process parameters. Excellent wetting between base material and filler was observed in all samples. Tensile specimens fractured at the base material in samples prepared using optimal brazing parameters. Microhardness tests performed on the cross-sections of joined samples indicated that joint zone hardness is higher than base material or copper filler. Examination using energy dispersive X-ray analysis revealed the presence of intermetallic compound Fe 5 Si 3 (Cu) in the joint as well as a small amount of copper inside the base material. The dispersal of fine Fe 5 Si 3 (Cu) particles in the joint is the main strengthening factor. The Fe 5 Si 3 (Cu) particles were determined to arise from three sorces: whiskerlike fragmentation, dissolve-separation, and anode spot action.MST/6157

Galvanised steels have been joined using an arc brazing process with Cu 97 Si 3 as the filler metal. The arcing time ranged from 1 s to 5 s with arcing current of 70 A in flowing argon. Excellent wetting between the base materials and the filler was observed for all samples. The reaction and products were confirmed by analysis of possible reaction products at the interface using thermodynamics, SEM, and EDS methods. From this, the schematic cycle of the interface Fe/Si compound growth mechanisms and fragmentation mechanisms of a whiskerlike intermetallic compound were determined. It has also been observed that Fe 5 Si 3 (Cu) particles are most likely to be generated at the interface through 'dissolve separation' 'whiskerlike compound fragmentation', and 'anode spot action' methods in the present arc brazing process.

AbstractThe B2O3-SiO2-Al2O3-CaO brazing fluxes and slags were investigated by using X-ray photoelectron spectroscopy (XPS) and Fourier transform infrared spectroscopy (FTIR). The microstructure of the fluxes and slags and its transformation mechanism during the brazing process were investigated, especially the effect of ratio of B2O3to SiO2(B2O3/SiO2) on the microstructural transformation was analyzed. The results show that the structure units of the fluxes and slags are [BO4], [BO3], [SiO4], [AlO4] and [AlO6], and the network structure is a silicon-boron network structure. The O in the slags consist of bridged oxygen, non-bridged oxygen and free oxygen. During the brazing process, part of the [BO4] in slag combined with silica-oxygen network to form Si-O-B structure, which contribute to the network structure of slag, and another part of the [BO4] was transformed to [BO3]. The increase of (B2O3/SiO2) contribute to the transformation of [BO4] to [BO3], and more B2O3 take part in the interface reaction with the increase of (B2O3/SiO2). Therefore, the increase of (B2O3/SiO2) leads to the decrease in the viscosity of the slag, which is beneficial to the spreading behavior during the brazing process.

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