Strength-ductility materials by engineering coherent interface at incoherent precipitates

Abstract

Abstract In the quest for excellent light-structural materials that can withstand mechanical extremes for advanced applications, design and control of microstructures beyond current material design strategy become paramount. Here, we design a coherent spinodal decomposition shell at incoherent precipitates in the 2195 aluminum alloy with multi-step metastable phase transitions. A high local strain rate via a neoteric deformation-driven metallurgy method facilitated the uphill diffusion of Li. The original T1 (Al2CuLi) phases were transformed into coherent-shell (Li-rich) coated incoherent-core (Al2Cu) precipitates. The ultimate tensile strength and elongation reached 620 ± 18MPa and 22.3 ± 2.2%, exhibiting excellent strength-ductility synergy. A new "incoherent-coherent interact" strain-hardening mechanism was clarified, which was believed to be promoted in other heat-treatable alloy systems, especially with multi-step metastable phase transitions.