Materials design workflow for extreme environments via computational method: Transition metal-doped (Hf0.5Ta0.5)C

The development of materials such as superalloys, ceramics, and composites for use in extreme environments poses major challenges owing to difficulties associated with those environments, including thermal shock and oxidation. Much research is focusing on optimizing compositions to withstand these conditions. In the present work, a computational workflow for designing compositions was developed. The method was applied to (Hf 0.5 Ta 0.5 )C, a representative material suited to extreme environments, but which suffers problems under oxidation conditions due to the low melting point of Ta 2 O 5 . Twenty-two potential transition-metal doping elements were screened, and Ti, Zr, Nb, and W were selected because of the excellent mechanical properties of the resulting solid solutions. Ab initio molecular dynamics simulations of oxidation showed that Ti and Zr doping could improve resistance to oxidation by promoting the oxidation of Hf and slowing that of Ta in the (Hf 0.5 Ta 0.5 )C. Additionally, Ta, Zr, and Nb doping increased the relative mobility of Hf, which supported sustained Hf oxide growth, as confirmed by nudged elastic band calculations. The results indicate that the appropriate selection of doping elements can enhance the performance with (Hf 0.5 Ta 0.5 )C, demonstrating the utility of the proposed composition design workflow.