Enhancing Fatigue Crack Growth Resistance in Heterostructured Aluminum Bimetals by Tailored Interface Design

Damage tolerance is a key requirement for structural materials subjected to cyclic loading, particularly in safety‐critical engineering applications. Heterostructured materials, especially laminated metallic composites (LMC), offer a route to improve fatigue performance through interface‐driven deformation mechanisms beyond those available in monolithic alloys. In this work, heterostructured aluminum bimetals with a single tailored interface were fabricated by roll bonding, enabling variations in hardness mismatch and microyielding behavior. Loading–unloading–reloading (LUR) tensile tests were combined with three‐point bending fatigue experiments to correlate microyielding characteristics, plastic zone development, and fatigue crack growth (FCG) behavior. Compared to the monolithic reference materials, the bimetals exhibit a reduction in FCG rates in crack‐arrester orientation. This improvement depends on hardness gradient and microyield strength mismatch across the interface. Postmortem crack path analyses reveal interface‐controlled toughening mechanisms, whose occurrence increases with stress intensity range and plastic zone size. The results indicate that a single engineered interface can reduce the FCG rate of the investigated bimetals relative to the reference materials, although the magnitude of this reduction depends on the mechanical property mismatch across the interface and the applied stress intensity range, with the strongest improvements observed for large mismatches at low stress intensities.