Hierarchical Chemical Ordering Enables Ultra-Efficient Strengthening and Multifunctionality.

Abstract

Modern alloy design increasingly seeks substantial strengthening with minimal alloying to improve sustainability while preserving or enhancing matrix functionality, an imperative for high-end applications like biodegradable implants. Yet for over half a century, strengthening has relied on introducing intensive defects via heavy alloying to impede dislocations; unfortunately, those defects inevitably induce functional degradation, producing a persistent strength-functionality trade-off. Here, we transform grain boundary (GB) sliding, typically a source of softening, into an ultra-efficient strengthening mechanism via engineered hierarchical chemical ordering (HCO). In a model biodegradable near-pure Zn alloy with only 0.17 at.% solute (Zn-0.12Mg-0.05Mn), yield strength increases tenfold to 350 MPa and represents the largest gain for ultra-lean alloys below 0.5 at.% while exceeding clinical benchmarks. The alloy delivers 32% elongation and uniform biodegradation that exceeds even what was long considered exclusive to pure metals, with 10%-37% higher cell viability, 38% enhanced wound healing, and uncompromised electrical conductivity. The HCO achieves dual-range strengthening as intragranular Mn-rich nanoclusters elevate GB motion stress by ∼164% through long-range suppression of stress relaxation, while Mg segregation at GBs increases critical sliding stress by ∼600% via short-range pinning. This mechanism bypasses traditional strength-functionality trade-offs, establishing a new design paradigm for ultra-lean, high-performance alloys.