An ab initio investigation of the effect of alloying elements on the elastic properties and magnetic behavior of Ni 3 Al Aakash Kumar a , Aleksandr Chernatynskiy b , Minki Hong b , Simon R. Phillpot a , Susan B. Sinnott a,⇑ a Department of Materials science and Engineering, University of Florida, Gainesville, FL 32611-6400, United States b School of Chemistry and Biochemistry, Georgia Institute of Technology, Atlanta, GA 30332-0400, United States article info Article history: Received 8 October 2014 Received in revised form 3 January 2015 Accepted 7 January 2015 Keywords: Density functional theory Ni-based superalloys Ni 3 Al Dopants Defect formation energy Elastic constants Bulk modulus abstract First principles density functional theory calculations were performed on pure and doped Ni 3 Al. The dopants investigated were Cr, Zr, La and Ce at concentrations of 3.13, 6.25 and 9.38 at.%, and B was con- sidered at concentrations of 3.03, 5.88 and 8.57 at.%. The defect formation energies, doping site prefer- ences, and elastic properties of pure and doped Ni 3 Al were determined and compared to published theoretical and experimental results. The magnetic properties of Ni 3 Al and, where appropriate, the dopants, were always taken into account, as the elastic constants predicted from spin-polarized and non-spin-polarized calculations were significantly different. The results were successfully correlated to the electronic structure through the electronic density using Miedema’s established model (Miedema et al., 1973). The calculations revealed that Cr doping increases the bulk modulus of Ni 3 Al and that all the other dopants considered decrease it. Ó 2015 Elsevier B.V. All rights reserved. 1. Introduction Nickel-based single crystal superalloys have become the most widely used alloys for high temperature applications, such as the blades of gas turbines. A key alloying element in the superalloys is aluminum as manufacturing of these alloys involves their pre- cipitation hardening [1] through the formation of the Ni 3 Al, the so-called c 0 phase. This precipitate occupies a volume fraction of about 70% in the alloy and is primarily responsible for its high strength under extreme conditions; the yield strength increases with increasing temperature up to a limit of around 880 °C [2]. In addition to Al, no less than 10 additional alloying elements are added to superalloys to further improve their chemical and mechanical properties, resulting in a complex final composition. For example, W provides solid solution strengthening [2], Cr has an additional role of improving oxidation resistance [2], B improves ductility [3], and Re improves creep resistance [4]. While some of these elements, including Cr and Re, partition preferentially to the c-Ni matrix, which is a solid solution phase, others, such as Ta and Al, prefer the c 0 phase [5,6]. The majority of the alloying elements used to dope Ni 3 Al are transition metals. The behavior and properties of these metals in Ni 3 Al has been extensively explored in recent studies [7–12] both experimentally and computationally. For example, Cr is responsi- ble for improving the elastic strength as well as providing oxida- tion resistance [13]. Zr is an important addition in the recent fourth and fifth generation superalloys along with B, as these ele- ments provide solid-solution strengthening and grain boundary strengthening, respectively. Zr also increases the critical resolved shear stress (CRSS) on the (1 0 0) plane of the c 0 phase thereby rais- ing the temperature where cross-slip transfer occurs, whereby a screw dislocation moves from one slip plane to another. Here, the movement is from the (1 1 1) planes to the (1 0 0) planes [14]. Moreover, Zr has been shown to improve creep-resistance by increasing the eutectic fraction of c–c 0 [15]. While some dopants, such as Cr, W and Ta, increase the bulk modulus, others, such as Zr, decrease it [7,8]. However, there is little information in the lit- erature regarding the variation of the various elastic properties with dopant concentration or alloy temperature. Mishima et al. [16,17] determined Young’s modulus of Ni 3 Al doped with different types and concentrations of transition metals by measuring the speed of sound in the doped alloy. In the case of transition metal dopants, Young’s modulus increased linearly with dopant concen- tration for Ti, V, Mo and W, changed little for Nb, and decreased for Hf and Ta. For the semimetal dopants (Si, Ge, Ga, and In), Young’s modulus decreased uniformly with dopant concentration. How- ever, the magnetism of the material was not discussed, which is http://dx.doi.org/10.1016/j.commatsci.2015.01.007 0927-0256/Ó 2015 Elsevier B.V. All rights reserved. ⇑ Corresponding author. E-mail address: ssinn@mse.ufl.edu (S.B. Sinnott). Computational Materials Science 101 (2015) 39–46 Contents lists available at ScienceDirect Computational Materials Science journal homepage: www.elsevier.com/locate/commatsci