Elastic Properties of B2-NiAl with W addition: A first-principles study

The effect of tungsten alloying on the elastic properties of B2-NiAl at low-temperature and high-temperature distribution of W atoms on sublattices. By means of the exact muffin-tin orbitals method in conjunction with the coherent potential approximation, the constants C$_{11}$,C$_{12}$,C$_{44}$, Young's modulus $E$, shear modulus $G$, Cauchy pressure values, $G/B$ ratios are calculated. Using phenomenological criteria of the correlation between ductility and elastic properties of solution phases, it has been shown that the addition of tungsten could yield improved ductility for B2-NiAl in both types of alloys. It is established that with the high-temperature distribution of W atoms on the Al sublattice, there is a loss of mechanical stability and a decrease in mechanical properties with increasing W concentration. In alloys with a low-temperature distribution of tungsten atoms between Al and Ni sites a unique combination of properties occurs: in addition to the ductility enhancement, a simultaneous increase of the elastic constants C$_{44}$ and C$_{11}$, shear modulus $G$, Young's modulus $E$ with increasing W content is observed. The differences in the behavior of elastic constants in alloys with different types of tungsten distribution on NiAl sublattices are analyzed by calculating the density of electronic states.