Effects of Pt on the elastic properties of B2NiAl: A combined first-principles and experimental study

First-principles calculations were performed to investigate the effects of Pt addition on the elastic properties of B2 NiAl. By correlating single-crystal elastic constants with point defect concentrations in the context of the Wagner-Schottky model, a general equation is proposed to calculate elastic properties of ternary B2 NiAl-Pt alloys as a function of alloy composition, in which the defect formation parameters were obtained from first-principles supercell calculations. At constant Al content, the calculations showed that the addition of Pt to B2 NiAl will increase its bulk modulus B but decrease both its shear nioduli C' and C-44. Results from the model calculations were found to be in good agreement with experimental measurements on polycrystalline samples, as well as direct first-principles calculations on special quasirandom structures. (c) 2006 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.