Brazeability of cold rolled three layer Al–7.5Si/Al–1.2Mn–2Zn–(0.04–1.0)Si/Al–7.5Si (wt.%) clad sheets

The effect of silicon content in the core alloy on the brazeability of three layer aluminium clad sheets was investigated using the clad sheets composed of Al–7.5 wt.% Si alloy (filler, thickness: 10 μm)/Al–1.2 wt.% Mn–2 wt.% Zn based alloy containing 0.04–1.05 wt.% Si (core, 80 μm)/Al–7.5 wt.% Si alloy (filler, thickness: 10 μm). It was revealed that the clad sheets with 0.04–0.64 wt.% Si core have an excellent sagging resistance (brazeability) with a limited erosion owing to the formation of a coarsely recrystallized grain structure in the core during brazing. In contrast, if the Si content in the core increased to about 1%, the sagging resistance of the clad sheets decreased with severe erosion due to an incomplete recrystallization of the core during brazing.