Strengthening and ductilization effect of boron in L12-type high-entropy intermetallic compounds

As a promising candidate for high-temperature structural materials, L1₂-type high-entropy intermetallic compound (HEIC) still encounters the problem of room-temperature brittleness. Microalloying with boron has been demonstrated to be an effective strategy for improving the ductility of HEICs. Nevertheless, the precise influence of boron on the microstructure and mechanical properties of HEICs remains unclear. To better understand the role of boron, a seires of Ni-Co-Fe-Cr-Al-Ti HEICs with varying boron concentrations (0.1–2.0 at.%) were systematically investigated. when the boron content is below 1.0 at.%, the HEIC exhibited a nearly single-phase L1₂ ordered structure. However, at higher boron concentrations, TiB₂ particles began to form at grain boundaries and interdendritic regions. Solute boron showed significant solid solution strengthening on the HEICs with a strengthening potency of approximately 270 MPa/at%. Appropriate boron doping effectively improved the ductility of L1₂-type HEICs by enhancing the grain boundary cohesion, with the highest ductility achieved at 0.5 at.% boron doping. The formation of TiB₂ particles had a negligible effect on yield strength, but adversely affected ductility. These findings deepen our understanding of the strengthening mechanisms in L1₂-type HEICs and provide valuable guidance for the design of novel HEICs.