Mechanisms of Liquid Film Migration (LFM) in Aluminum Brazing Sheet

The phenomenon of liquid film migration (LFM) in aluminum brazing is described in a companion paper ^[1]. To clarify the mechanism, the effect of core alloy homogenization, cold work prior to brazing, and brazing temperature on the LFM kinetics has been studied. Based on microstructures, LFM kinetics, and concentration profile data, factors influencing the migration rate of liquid films have been analyzed. Several possible driving forces for LFM are proposed: (1) coherency strain energy, (2) reduction of particle/matrix interfacial energy, and (3) reduction of energy in recovered dislocation structure or subgrain boundaries in the case of lightly cold worked brazing sheet.