Abstract: In order to improve the fatigue performance and extend the fatigue life of the aluminum plate-fin heat exchanger used in liquefied natural gas (LNG) applications, based on fatigue testing and fracture morphology analysis methods, the fatigue fracture morphology characteristics of the typical areas of the main material Al3003 are compared and analyzed through macroscopic and scanning electron microscopy observations, and the fatigue mechanism of Al3003 is explored. The results indicate that the average fatigue lives of Al3003 under high and low cyclic stresses are 1.92×10⁴ cycles and 4.79×10⁶ cycles, respectively. The fatigue zone of Al3003 exhibits a similar crack propagation process under high and low cyclic stresses, but its area and number of internal fatigue sources are different. There is only one fatigue source inside the specimen under high cyclic stress, whereas there are two main fatigue sources and numerous small fatigue sources inside the specimen under low cyclic stress. The critical zone of Al3003 under high and low cyclic stress has similar overall morphology characteristics, but its slip bands and tearing morphology are different in density. The instantaneous fracture zone of Al3003 under high and low cyclic stress has similar morphological characteristics; however, the proportion of its extension morphology in the instantaneous fracture zone is different.

Key words: aluminum plate-fin heat exchangers, Al3003, fatigue life, fracture mechanism, fracture morphology