Strengthening mechanism of aluminum on elastic properties of NbVTiZr high-entropy alloys

Understanding of strengthening is significant to improve the mechanical properties of high-entropy alloys (HEAs). Taking Al element as a prototype, we show that the Al-induced strengthening phenomenon in NbVTiZrAl HEAs cannot be explained by elastic interaction induced by lattice and modulus effects on the basis of our ab initio calculations. From the calculated mechanical properties and chemical bonding of NbVTiZrAl_x HEAs, we highlight that the Al-induced strengthening is mainly due to the strong angular characteristic bonds between the introduced aluminum and transition metal atoms, but rather than the mismatch of atomic size and modulus between Al and the other components in NbVTiZrAl_x alloys. Our findings provide new insight for the design and improvement of HEAs and complementary information to the alloying effects.