Atomic faulting drives exceptional toughness in low thermal expansion chromium alloys

Abstract

Abstract Endowing functional properties with mechanical responses in traditional metals has been a frontier topic, akin to transforming base metal into gold. Chromium and its alloys, with their functional deficiencies and limited ductility, serve as typical examples. Herein, we report a Cr 96 Fe 4 Ge 1.3 B 1 alloy that unifies low thermal expansion (LTE, α l  = 1.79 × 10 -6  K -1 , 200 − 315 K) with exceptional toughness (240.2 J·cm -3 ). The enhancement in mechanical responses is primarily attributed to layered Cr 2 B intermetallic precipitates, which ameliorate interfacial cohesion and simultaneously refine the grain structure. The weakened interlayer interactions within the Cr-B layers facilitate the nucleation and movement of numerous tiny stacking faults in precipitates, efficiently alleviating strain energy and resulting in marked work-hardening ability. Additionally, antiferromagnetic fluctuations in the BCC matrix contribute to the unique LTE behavior. This paves the way for the design of high-performance alloys featuring layered-symmetry precipitates.