Study of the nano-structured nickel-based brazing filler synthesized by mechanical alloying

A series of BNi-2 nickel-based brazing fillers were synthesized by mechanical alloying (MA) the appropriate proportion of pure elements in a high-energy ball mill. The results of DTA show an exothermic peak around 700 K, which is presumed to be a metastable phase, for the alloy after 4 h milling. After 10 h milling, the final particle size of the powder can reach about 20 μm and exhibits a quite even equiaxed shape. The structural evolution with milling time by X-ray diffractometry shows the following transformation: mixture of pure elemental powders→microcrystalline f.c.c. solid solution→nanocrystalline f.c.c. solid solution. The crystal size calculated by X-ray diffraction was about 5 nm for the powder after 10 h milling. This is in very good agreement with the evidence of nanocrystalline phase obtained by TEM observation. In addition, the evaluation of the brazing properties of the BNi-2 powder synthesized by MA is similar to the gas atomized BNi-2 powder.