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  Guo, Y.; Gong, Y.; Lu, Z.; Miao, X.; Nie, J.; Xu, F.; Caron, L.: Ductile behavior of Hf₂Ni₇ intermetallic phase in FeCoNiHfx complex concentrated alloys. Journal of Alloys and Compounds 1048 (2025), p. 185277/1-9

10.1016/j.jallcom.2025.185277

Abstract:
In this study, the phase constitution and mechanical behavior of FeCoNiHfx complex concentrated alloys (CCAs) were investigated. The microstructure evolves from a single FCC solid solution at x = 0 to a eutectic BCC + Hf2Ni7 microstructure at x = 0.3. This phase constitution differs from that of most eutectic 3d-4d CCAs, which are usually consisted of FCC (or BCC) and hard Laves phase. More importantly, the Hf2Ni7 phase, containing a high density of stacking faults, cooperates with a short-range-ordering BCC phase to simultaneously enable an optimal combination of strength and ductility in the eutectic FeCoNiHf0.3. The FeCoNiHf0.3 exhibits a compressive strength of 1064.24 MPa and a strain exceeding 22.5 %, the optimal mechanical properties in our FeCoNiHfx system. The mechanical properties of FeCoNiHfx deviate from the typical strength-ductility trade-off commonly observed in the other 3d-4d CCAs, demonstrating combination of ductility and strength at the eutectic point. This work highlights the critical relationship between reduced configurational entropy, the stability of intermetallic phases, and cooperative deformation mechanisms. The findings advance the understanding of CCA design principles and shed light on developing novel eutectic CCAs with synergistic high strength and high ductility.