Material-Gradient Enabled Enhancement of Strength and Strain-Hardening of Lattice Structures

Additive manufacturing enables the creation of architected lattices with tailored mechanical responses, yet conventional geometry-driven designs often suffer from structural redundancy and limited adaptability. Here, spatially continuous material gradients are introduced into body-centered cubic (BCC) truss and Gyroid triply periodic minimal surface (TPMS) lattices using a custom laser powder bed fusion platform capable of alloy composition control. This strategy decouples mechanical tuning from geometry, enabling programmable deformation through material distribution alone. Compression experiments reveal that continuous gradients fundamentally reconfigure the collapse mechanism, guiding a stable plastic front from softer to stiffer regions. This controlled strain propagation enhances structural performance, increasing plateau stress and energy absorption by up to 23.6% and 25.4% in BCC lattices, and 9.8% and 12% in Gyroid structures, respectively, compared to sharp-interface counterparts. These improvements arise from suppressed localization and stabilized plastic flow, effectively imparting an emergent strain-hardening behavior at the macroscale, even in base alloys with limited intrinsic hardening. These findings establish material gradients as a powerful design axis for metamaterials, advancing beyond passive shape optimization toward active, composition-driven performance control.