Tailoring modulus and hardness of AuAgCu alloys via three-dimensional coherent dual-phase structures

Tailoring elastic modulus of alloys or composites is typically achieved through composite or solute effects. In this work, we demonstrate that simultaneous enhancement of elastic modulus and hardness in Au50Ag20Cu30 alloys can be realized via elastic strain engineering, enabled by three-dimensional coherent dual-phase structures (3D-CDSs) which was self-organized through spinodal decomposition. Microstructural characterization and nanoindentation testing confirm the alternating hydrostatic compressive or expansion strains associated with the coherent dual-phase structure. This strain modulation leads to significant enhancements in elastic modulus (by 27%) and hardness (by 37%) compared to solid solution phase. These results are consistent with theoretical predictions and molecular dynamics simulations. Our study presents a rational and effective strategy to simultaneously tailor high elastic modulus and mechanical strength through 3D elastic strain engineering. By simultaneous tuning of modulus and hardness via three-dimensional coherent dual-phase structures, this work reveals the relationship between nanoscale phase structures, lattice strain, and mechanical response, enabling high-modulus and hardness within a model AuAgCu alloy.