Multicomponent Ni-rich high-entropy alloy toughened with irregular-shaped precipitates and serrated grain boundaries

A novel precipitation-strengthened multicomponent Ni-rich Ni_46.23Co₂₃Cr₁₀Fe₅Al_8.5Ti₄W₂Mo₁C_0.15B_0.1Zr_0.02 (at.%) high-entropy alloy (HEA) was designed with strain-hardening after yielding rather than strain-softening even at the temperature of 1000°C. Due to the rapid onset of intergranular cracking, the HEA with spherical precipitates and straight grain boundaries was brittle, exhibiting an inferior tensile strength of ~220 MPa, and an insufficient uniform elongation of only ~1.9%. The serrated-grain-boundary architecture effectively overcomes this intergranular cracking issue. The resultant HEA with irregular-shaped precipitates and serrated grain boundaries showed a brittle-to-ductile transition, giving in a superior strength up to as high as ~260 MPa while maintaining a uniform elongation of ~6.5%. Such an improvement of the strength and ductility has been attributed to the enhanced resistance of the serrated grain boundaries to the intergranular crack nucleation and propagation. Our current results provide a new method for the innovative design of high-temperature structural materials with superior mechanical performances.