Fatigue crack initiation and propagation of wire arc additive manufactured Al-Mg alloy

Abstract

Wire arc additive manufacturing technology has many advantages in producing large engineering structures and is being applied in aerospace structures. It is necessary to explore the fatigue failure mechanism of wire arc additive manufactured aerospace aluminum components to ensure these structures' safe application. Crack initiation and propagation behavior for wire arc additive manufactured Al-Mg alloy are investigated under fatigue loading. The microstructure characteristics of different regions are analyzed by metallographic and electron back-scattered diffraction measurements. The fatigue test results show that multi-crack initiation is the fatigue damage characteristic for the additive manufactured parts. The small cracks are distributed in the deposition and layer band zones, and the number of small cracks increases with the cyclic numbers. The main crack initiates from the coarse columnar grain boundaries in the deposition zone, and the final fracture is in the strain concentration zone. The fatigue fracture morphologies show that the fatigue cracks initiate at the pores, non-melted particles, and grain boundaries.