This work was carried out at temperatures of 1100 -1140°C for holding times in the range 10 -90 s. The solution mechanisms of the base metals of the Ti/Fe contact reaction couples and the growth rules of the Ti-Fe compound and b-Ti(Fe) were studied. The results show that the solution process of the base materials is transient, counted by the time in Ti/Fe contact reaction couples. It can be seen that the quantities of the Ti -Fe compound and b-Ti(Fe) can be reduced effectively through controlling the holding time. When temperature is 1100°C and the holding time is less than 10 s, there is no coarse block Ti -Fe compound in the contact reaction liquid phase zone, and the growth process of the lamellar b-Ti(Fe) experiences a latent period. When the holding time reaches 30 s, the density of the lamellar b-Ti(Fe) reaches a maximum value. The thickness of the liquid phase zone reaches 60 mm at a temperature of 1100°C and a holding time of 10 s.
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
The growth process of Ti ± Cu compound at the interface of a Ti ± 6Al ± 4V/72Ag ± 28Cu (wt-%) joint was analysed using X-ray diffraction, SEM, and energy diffraction spectra. According to the investigated results, when the joint was brazed for a relatively short holding time, atoms of Ti and Cu diffused into the interface would combine into Ti 2 Cu by eutectoid reaction during the cooling stage. As the holding time is beyond the critical brazing time, Ti 2 Cu compound decomposed owing to a large amount of Ti in the base metal dissolving into the brazing zone and the relatively gentle concentration gradient of Cu, thus resulted in the solid dissolving of Cu into Ti. In this case, the resulting joints exhibited high strengths. On the basis of the analysis mentioned above, a concept `critical brazing time' was proposed.MST/5185
Contact reactive brazing on 6063 Al alloy has been conducted by using Cu foil or Cu foil-Mg powder-Cu foil multilayer as interlayer. The microstructures of the joints and grain boundary penetration phenomenon were analysed and discussed primarily. The results showed that the microstructure of the reaction zone consisted of a-Al solid solution and CuAl 2 compound as monolayer Cu foil was used, and meantime, obvious grain boundary penetration phenomenon at the reaction interface was found. However, the reaction zone of the joint bonded with Cu foil-Mg powder-Cu foil was composed of Al(Mg,Cu) solid solution, CuAl 2 intermetallic compound, Cu-AlMg ternary intermetallic compound and Al 2 MgO 4 . It was also found that the grain boundary penetration phenomenon was delayed as Mg powder was added into the interlayer.
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