Effects of Ti, Zr, Ta, and W on elastic properties, stacking fault energy, and ductility of HfC

First principles calculation is carried out to systematically investigate the effects of transition metal elements (Ti, Zr, Ta, W) on elastic properties, hardness, surface energy, stacking fault energy , and ductility of HfC. It is found that the addition of Ti and Zr would decrease the elastic properties and hardness of HfC, while Ta and W could increase. Calculations also reveal that Ti, Zr, and W decrease both surface energy and stacking fault energy of HfC, and such a decrease is mainly attributed to smaller bond energies of Ti-C, Zr-C, and W-C bonds than that of Hf-C. The addition of Ta increases the surface energy of HfC due to a stronger Ta-C bond, and decreases the stacking fault energy of HfC as a result of a more reduction of bond energy of the Ta-C bond than that of the Hf-C bond. In addition, Ta and W have an important effect to considerably increase the ductility of HfC, while such effects of Ti and Zr are much smaller.