High-Entropy Alloys Including 3d, 4d and 5d Transition Metals from the Same Group in the Periodic Table

Exact equi-atomic senary alloys including three elements from 3d, 4d and 5d transition metals (TMs) were investigated for their ability to form solid solutions as high-entropy alloys (HEAs). Three alloys of CoCuPdTiZrIIf, CoCuFeTiZrIIf and AgAuCuNiPdPt were selected by focusing on (Ti, Zr, lift from Early-TMs, and (Cu, Ag, Au) and/or (Ni, Pd, Pt) from Late-TMs based on an alloy design with a help of Pettifor map for binary compounds with several stoichiometries and binary phase diagrams, together with a marginal Al(4)CoNiPdPi alloy. the XRD analysis revealed that the CoCuPdTiZrHf alloy was formed into a bcc, whereas both the CoCuFeTiZrElf and AL(4)CoNiPLIPt alloys were a (and the AgAuCuNiPdPt alloy was dual fcc structures. The observations with optical and scanning-electron microscopes and analysis with energy dispersive X-ray for chemical composition revealed the homogeneous morphologies of these alloys in micrometer scale. The types of crystalloeraphic structures of the CoCuPdTiZrIIf, CoCuFeTiZrIIf and AgAuCuNiPdPt HEAs and the Al4CoNiPdPt alloy can be principally explained by valence electron concentration. Three constituent elements from TMs in the same group enhance the increase in the number of complete solid solutions in the constituent binary systems, leading to forming these HEAs.