Ti and Nb Addition to Ni3Al: Site Preferences and Alloying Efficiency from First Principles Calculations
The first principles calculations were performed to study the sit preferences and effects on elastic properties with the Cambridge sequential total energy package (CASTEP) code for the Ni3Al system doped with the alloying element M (Ti, Nb). It was found that all the alloying elements were preferred to replace the Al sites but Ni sites at 0 K. element M (Ti, Nb) would increase the bulk, shear and Young’s modulus in Ni3Al poly-crystalline alloy, and decrease the bulk/shear modulus ratios (B/G), while all of which were larger than 1.75, indicating that Ni3Al, Ni24Al7Nb and Ni24Al7Ti poly-crystalline alloys were ductility materials. Through analyzing the electronic Structure of the calculated Ni3Al alloys, we found that the covalent bonds between alloying atom M (Ti, Nb) and their neighbor atoms Ni were considered to be the mainly strengthening mechanism of alloying elements M in Ni3Al alloys.
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