Phase field and room-temperature mechanical properties of C15 Laves phase in Nb–Hf–Cr and Nb–Ta–Cr alloy systems

The pseudo-binary NbCr2–HfCr2 Laves phase alloys exhibited a large off-stoichiometric range while the pseudo-binary NbCr2–TaCr2 Laves phase exhibited a limited off-stoichiometric range. The fracture toughness of the ternary Nb–Hf–Cr and Nb–Ta–Cr Laves phase alloys was higher than those of the binary NbCr2, HfCr2 and TaCr2 Laves phase alloys, and decreased in the (Nb,Hf)-rich region of the C15 Laves phase. Depending on the alloying species and associated defect structures, room-temperature toughness of the C15 phase can be beneficially or deleteriously affected.