Superior strength and ductility synergy at elevated temperatures of LPBF-fabricated IN718 + HfB2 through cooperative microbands and microtwins

Laser-powder bed fusion (LPBF) fabricated IN718 superalloy is often constrained by its inferior high-temperature performance beyond 650 °C. While ceramic reinforcement is a widely adopted strategy to address this limitation, conventional ceramics (e.g., ZrB 2 , Y 2 O 3 ) often suffer from interfacial instability and insufficient effectiveness at elevated temperatures. This study presents a superior alternative by incorporating nano-scale HfB 2 particles to develop a high-performance IN718 composite via LPBF. The novel IN718 + HfB 2 composite demonstrates an exceptional balance between ultra-high strength and ductility at both ambient and elevated temperatures. At 650 °C, the composite exhibits a high ultimate tensile strength (UTS) of 1178.2 MPa and elongation of 8.6%. At 800 °C, the composite maintains an ultra-high UTS of 732.5 MPa and elongation of 6.6%, surpassing most reported IN718-based composites. The outstanding strength is attributed to the in-situ formation of a continuous cellular network of borides and intermetallics during LPBF, which synergistically enhanced grain boundaries, dislocations, and precipitates strengthening capabilities. Moreover, these uniformly distributed precipitates facilitated a unique cooperative deformation behaviors of microbands and microtwins at elevated temperatures. Consequently, this study offers a new pathway for achieving superior mechanical properties for nickel-based superalloys beyond conventional reinforcement strategies.