Si diffusion from cladding layer to core material easily occurred in the composite brazing sheet of 4343/3005/4343 during brazing process

which affected the brazed joint formation and mechanical properties.Effects of core-material microstructure on diffusional solidification behavior in 4343/3005/4343 three-layer aluminum brazing sheet were investigated by DSC（differential scanning calorimetry）.The results show that molten 4343 cladding layer can be solidified completely with holing temperature at 605 ℃which is more than the melting point.The core material microstructure has the significant effect on the diffusional solidification process.The molten cladding alloy can completely solidified at 605 ℃ for 30 min when core material has fine equiaxed grains.Core material with coarse and long strip grains can greatly decrease the Si diffusion velocity as a result of small grain boundary density and high fraction grain boundary with low angle

which results in the 50% molten cladding materials solidification at 605 ℃ for 30 min

and the cladding layer can be completely solidified completely with holding for 120 min.