New pathways for corrosion-resistant steels with engineered mechanical performance via mesoscale design

Mesostructured steels, which combine distinct metallic phases in geometrically tailored architectures, offer new opportunities to engineer mechanical performance; however, their application in corrosive environments is challenged by the potential for galvanic interactions between dissimilar phases. The electrochemical compatibility and corrosion behaviour of such architectured multi-phase steels remain poorly understood. In this work, architectured 316 L/17-4PH stainless steel composites were fabricated via material extrusion-based additive manufacturing to generate alternating austenitic and martensitic domains. Mechanical testing confirms that mesoscale architecture promotes cooperative deformation and improved macroscopic mechanical performance through controlled local strain redistribution. Corrosion testing and scanning Kelvin probe measurements reveal that, despite measurable electrochemical potential differences between constituent phases, interfacial elemental diffusion smooths compositional transitions and mitigates galvanic effects. As a result, the corrosion resistance of the composite remains comparable to that of monolithic 17-4PH, even under aggressive test conditions. These findings demonstrate that mesoscale architectural design can be used to engineer galvanically compatible multi-material stainless steels, providing new insights into the corrosion behaviour of architectured metallic systems and opening new opportunities for multifunctional structural materials.