A novel coherent particles-reinforced FCC-based high-entropy superalloy with superior high-temperature compressive properties

A novel κʹ-strengthened FCC-based Al0.5CoFeNiC0.1 high entropy superalloy (HESA) with minor B2 phase was prepared by arc melting. The FCC/κʹ dual-phase microstructure with thermal stability is similar to γ/γʹ microstructure of Ni-based superalloys. Surprisedly, the large volume fraction (nearly 50%), high density and nano-scale coherent κʹ particles with uniform distribution are easily accessible only by direct solidification, which gives rise to superior compressive yield strengths at both room and elevated temperatures, reaching 1130 MPa at 25 °C and 830 MPa at 700 °C, respectively. The sustained high-temperature yield strength is contributed to both the antiphase boundaries (APBs) and stacking faults (SFs) shearing κʹ particles. Further, optics and electron microscopy analyses revealed the changes (transition point about at 0.6 Tm, where Tm is melting temperature) of the dominant deformation and failure mechanisms, dependent on the temperature. The dominant deformation mode is planar slip and SFs at relatively low temperatures, while the cross slip and dislocation dissociation above 800 °C (0.6 Tm), coupled with the diffusion-controlled recovery mechanisms. The failure mechanism shows failure mode from shearing fracture to thermal softening. Our κʹ-strengthened FCC-based superalloy provides a route for elevated-temperature applications.