Compositionally graded interfacial microstructure and corrosion behavior of 316 L/B30 multi-material bimetallic structure fabricated by laser powder bed fusion

The microstructure and corrosion behavior of the compositionally graded interface in 316 L/B30 dissimilar material joint structures were systematically investigated. The gradient interface characterized by dual-phase constituents consisting of α-Cu and γ-Fe phases achieves favorable metallurgical bonding with only minor defects existed in regions with 20–30 wt.% 316 L. The separated γ-Fe phase and α-Cu phase in the mixed composition zone show a complex and disordered distribution. The region containing 60–70 wt.% B30 exhibits most severe corrosion in various zones with different composition, indicating the influence of macro-galvanic effect in corrosion process. In addition, the micro-galvanic interactions between different phases also affect the corrosion behavior, where the γ-Fe phase predominantly acts as cathodic phase, inducing preferential anodic dissolution of adjacent α-Cu phase.