MICROSTRUCTURE AND BRAZING CHARACTERISTICS FOR THREE LAYER Al-Si/Al-Mn-Zn-Si/Al-Si BASED BRAZING SHEETS

초록

Three layer brazing sheets composed of Al-7.5Si alloy (filler, thickness:10)/Al-1.2Mn-2Zn-(0.04-1.0)Si alloy (core, thickness:80)/Al-7.5Si alloy (filler, thickness:10), were produced by laboratory fabrication, through casting, hot rolling, cold rolling, intermediate annealing and final cold rolling, in order to investigate effects of the Si content of core alloy and the reduction rate of final cold rolling on the microstructure and brazing behavior of the brazing sheets. It was revealed that the microstructure and brazeability of the brazing sheets are governed by both the Si content of core alloy and the reduction rate of final cold rolling. The excellent brazeability was obtained when the Si content of the core alloy was less than 0.7wt.% and the reduction rate of final cold rolling exceeded 20%. In this case, a coarsely recrystallized grain structure was developed in the core during brazing process, which suppressed the penetration of melting filler into the core.