Journal
ADVANCED THEORY AND SIMULATIONS
Volume 3, Issue 9, Pages -Publisher
WILEY-V C H VERLAG GMBH
DOI: 10.1002/adts.202000111
Keywords
DFT calculations; dislocation modeling; hardness; high-entropy carbides
Categories
Funding
- EPSRC (MASSIVE) [EP/L017695/1]
- National Natural Science Foundation of China [11674264]
- QMUL Research-IT
- Slovak Grant Agency for Science [VEGA 2/0163/16, VEGA 2/0091/18, APVV-14-0385, APVV-15-0469]
- M-ERA.NET2 (DURACER)
- Operational Program Research and Development through European Regional Development Fund [ITMS: 26220220186]
- China Scholarship Council
- EPSRC [EP/L017695/1] Funding Source: UKRI
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High-entropy carbides (HECs) are of great interest as they are promising candidates for ultra-high-temperature and high-hardness applications. To discover carbides with enhanced yield strength and hardness, mechanism-based design approaches are needed. In this study, dislocation core atomic randomness as a mechanism for hardness enhancement is proposed, in which the random interactions between different elements at a dislocation core make it more difficult for the dislocation to slip. The Peierls stress of an a/2 <(1) over bar 10 >{110} edge dislocation is calculated based on density functional theory, in which atomic randomness is increased by increasing the number of elements at the dislocation core. The results show that the Peierls stress statistically increases with increasing number of elements, indicating that incorporating more elements is likely to produce higher hardness. Based on this guiding principle, three eight-cation HECs are fabricated (Ti,Zr,Hf,V,Nb,Ta,X,Y)C (X,Y = Mo,W, Cr,Mo, or Cr,W), the composition of which is guided by ab initio calculations of their formation enthalpy and entropy forming ability. The single-phase dense ceramics all show high nanoindentation hardness of around 40 GPa. The random interactions between different elements at a dislocation core provide a mechanism for improving the hardness of structural ceramics.
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