In this work, the RM(Nb)IC alloy Nb-30Ti-10Si-5Cr-5Sn-3Fe-2Al-2Hf (NV2) was studied in the as-cast and heat-treated conditions; its isothermal oxidation at 700, 800 and 900 degrees C and its room temperature hardness and specific strength were compared with other Sn-containing RM(Nb)ICs-in particular, the alloy Nb-24Ti-18Si-5Cr-5Fe-5Sn (NV5)-and with RCCAs and RHEAs. The addition of Fe (a) stabilised Nb-ss; A15-Nb3X (X = Al, Si and Sn) and Nb3Si; metastable Nb3Si-m' and Nb5Si3 silicides; (b) supported the formation of eutectic Nb-ss + Nb5Si3; (c) suppressed pest oxidation at all three temperatures and (d) stabilised a Cr- and Fe-rich phase instead of a C14-Nb(Cr,Fe)(2) Laves phase. Complex concentrated (or compositionally complex) and/or high entropy phases co-existed with "conventional" phases in all conditions and after oxidation at 800 degrees C. In NV2, the macrosegregation of Si decreased but liquation occurred at T >1200 degrees C. A solid solution free of Si and rich in Cr and Ti was stable after the heat treatments. The relationships between solutes in the various phases, between solutes and alloy parameters and between alloy hardness or specific strength and the alloy parameters were established (parameters delta, Delta chi and VEC). The oxidation of NV2 at 700 degrees C was better than the other Sn-containing RM(Nb)ICs with/without Fe addition, even better than RM(Nb)IC alloys with lower vol.% Nb-ss. At 800 degrees C, the mass change of NV2 was slightly higher than that of NV5, and at 900 degrees C, both alloys showed scale spallation. At 800 degrees C, both alloys formed a more or less continuous layer of A15-Nb3X below the oxide scale, but in NV5, this compound was Sn-rich and severely oxidised. At 800 degrees C, in the diffusion zone (DZ) and the bulk of NV2, Nb-ss was more severely contaminated with oxygen than Nb5Si3, and the contamination of A15-Nb3X was in-between these phases. The contamination of all three phases was more severe in the DZ. The contamination of all three phases in the bulk of NV5 was more severe compared with NV2. The specific strength of NV2 was comparable with that of RCCAs and RHEAs, and its oxidation at all three temperatures was significantly better than RHEAs and RCCAs.
