Towards full-scaling tribology of heterostructured metals: A review

Friction and wear, long regarded as unavoidable penalties in mechanical systems, consume nearly a quarter of global primary energy. Metallic components in engines, turbines, and bearings therefore present both the greatest challenge and the greatest opportunity for efficiency gains. This mini-review surveys how heterostructured (HS) metals—encompassing gradient, laminate, and nanotwinned (NT) architectures—enable adaptive and self-stabilizing responses under diverse tribological conditions. Through engineered gradients in strength, periodic stacking of layers with distinct mechanical responses, and the incorporation of dense nano-twin populations, HS metals redistribute contact stresses, promote compatible heterogeneous plasticity, and delay the onset of surface degradation, leading to substantial reductions in friction and wear. Building on these mechanistic insights, we discuss a full-scaling tribological framework that links architectural descriptors (such as gradient depth and slope, laminate period, interface character, and twin spacing) to operational variables (such as contact radius, Hertzian stress, sliding velocity, and lubrication condition) and to friction–wear responses from nano- to macro-scales. Looking ahead, we highlight opportunities to integrate operando characterization, multi-scale simulations, and data-driven design to construct quantitative “design maps” for the tribological performance of HS metals. The convergence of heterostructure design with advanced fabrication routes is expected to yield microstructures that are not only strong and wear-resistant but also adaptive and robust under service-relevant conditions, pointing toward low-energy, long-life metallic friction interfaces. • Heterostructured architectures (gradient, laminate, nanotwinned) tailor tribo-induced subsurface stress fields, suppressing catastrophic strain localization. • Heterostructured metals can substantially reduce friction and wear relative to homogeneous counterparts. • A full-scale, architecture-to-performance tribological framework can link structural descriptors to multiscale contact mechanics.