Effect of corrosion pit on fatigue damage and failure in powder bed fusion AlSi10Mg

Abstract

This paper is concerned with environmental corrosion during service of load-bearing aluminum alloys fabricated by additive manufacturing (AM) with a focus on damage evolution characterization and identification of dominated failure mechanisms of pre-corroded selective laser melted aluminum alloy. An experimental strategy for analysis of the damage and failure process is presented, combining 3D surface measurement, 3D digital image correlation, and scanning electron microscopy, to provide a multi-source experimental characterization of corrosion morphology, strain field evolution, and fracture morphology. Statistics and machine learning methods were employed to process the measured multi-source experimental data, showing that local average roughness has a strong influence on macro-crack initiation position. The analysis focuses on four primary types of fatigue micro-crack initiation, namely, internal defect, diffuse corrosion, corrosion micro-pit, and corrosion jut; internal defect and diffuse corrosion are unique features for powder bed fusion (PBF) AlSi10Mg. The micro-crack initiation mechanisms for all four types are (i) local stress concentrations due to adjacent material micro-structural defects, (ii) interaction of underlying alloy microstructure and corrosion-induced stress/strain, and (iii) local stress/strain concentration at corrosion micro-pit and jut, respectively.