Sagging mechanisms in the brazing of aluminum heat exchangers

A sagging mechanism was investigated using a sagging test rig to evaluate the brazeability of an aluminum sheet. The results show that sagging was controlled by softening of the elastic modulus in the initial stage, followed by an accelerative sagging stage, which was induced by both the dissolution of nanoprecipitates and the softening of the elastic modulus. Abnormal grain growth, which is related to the amount of final cold-rolling reduction, is responsible for the cessation of sagging at the end of the sagging process.