Architecting new materials with strength-ductility synergy through interphase engineering

Conventional strategies to strengthen alloys are usually accompanied by drastic sacrifice in ductility, which is known as the strength-ductility trade-off. New metallurgical processing approaches are required to defeat this longstanding dilemma. Here we report a novel solid-state powder manufacturing route to overcome this challenge enabling the architecting of a complex multiphase constituent composite using readily available metal powder as a feedstock. The materials design philosophy is successfully verified in a system mixing conventional austenitic stainless steel and ferritic steel powder and consolidating it by hot isostatic pressing. Significant strengthening and work hardenability are achieved at no expense of ductility compared to the ferrite and austenite on their own. Such extraordinary strength-ductility synergy is attributed to the well-architected compositional gradients across different phases resulting in soft and hard regions at the scale of the original powder without sharp interfaces. Accordingly, plasticity progresses from soft to hard regions during mechanical loading, which is the key to mitigating the deformation incompatibility and enabling remarkable ductility. Our study provides a new concept for materials design with synergistic properties that used to be trade-offs in conventional materials, which is applicable to a broad range of material systems with unprecedented multifunctionality.