Brazing - a method of welding high silica aluminium

Brazing - a method of welding high silica aluminium

Brazing differs from fusion welding methods in that conventional brazing is a welding technique in which a brazing material with a lower melting temperature than the base material is used (or automatically generated during the process) and the operating temperature is taken to be below the solid phase line of the base material and above the liquid phase line of the brazing material. The workpiece is often heated as a whole or uniformly over a large area around the brazing seam, so that the relative deformation of the workpiece and the residual stresses in the welded joint are much lower than in fusion welding.

In today's manufacturing industry, high-silicon aluminium materials are generally used for high-precision components in the aerospace machinery industry. For these devices the impact on the workpiece is also minimal when brazing is used. As the high silicon aluminium alloy contains a hard silicon phase, the wetting performance of the brazing material on this series of materials is poor, and it is difficult to achieve an effective connection with ordinary soft brazing methods. Hou Ling et al. used the method of first chemically pre-plating Ni on the 65Si35A1 alloy substrate and then plating Ni-Cu-P, Au and Cu layers respectively to effectively improve its soft brazing performance in the brazing test. Several soft brazing materials such as Sn-Pb, Sn-Ag-Cu, Sn-In and Sn-Bi were used to analyse the soft brazing test in the furnace on 65Si35Al alloy specimens with different coatings, including the use of metallurgical microscopy, scanning electron microscopy with energy spectrum analysis (EDS) and other testing methods to examine the microstructure and morphology of the welded joints, the physical composition and so on, to explore the effect of brazing process parameters on the quality of brazed joints of 65Si35Al alloy was investigated, and the causes of macroscopic and microscopic defects in the joints as well as the differences in the wetting properties of the brazing material for different coatings were analysed.