Phase stability, elastic, and thermodynamic properties of the L1 2 (Co,Ni) 3 (Al,Mo,Nb) phase from first-principles calc
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i Shang Department of Materials Science and Engineering, The Pennsylvania State University, University Park, Pennsylvania 16802, USA
Kang Wang Department of Materials Science and Engineering, The Pennsylvania State University, University Park, Pennsylvania 16802, USA; and State Key Laboratory of Solidification Processing, Northwestern Polytechnical University, Shaanxi 710072, People’s Republic of China
Feng Liu State Key Laboratory of Solidification Processing, Northwestern Polytechnical University, Shaanxi 710072, People’s Republic of China
Yi Wang Department of Materials Science and Engineering, The Pennsylvania State University, University Park, Pennsylvania 16802, USA
Qiong Wang and Tong Lu National Supervising & Testing Center for Engineering Composite Materials’ Quality, Jiangsu Provincial Supervising & Testing Research Institute for Products’ Quality, Nanjing 210007, People’s Republic of China
Zi-Kui Liu Department of Materials Science and Engineering, The Pennsylvania State University, University Park, Pennsylvania 16802, USA (Received 28 July 2016; accepted 28 December 2016)
Phase stability, elastic, and thermodynamic properties of (Co,Ni)3(Al,Mo,Nb) with the L12 structure have been investigated by first-principles calculations. Calculated phonon density of states show that (Co,Ni)3(Al,Mo,Nb) is dynamically stable, and calculated elastic constants indicate that (Co,Ni)3(Al,Mo,Nb) possesses intrinsic ductility. Young’s and shear moduli of the simulated polycrystalline (Co,Ni)3(Al,Mo,Nb) phase are calculated using the Voigt–Reuss–Hill approach and are found to be smaller than those of Co3(Al,W). Calculated electronic density of states depicts covalent-like bonding existing in (Co,Ni)3(Al,Mo,Nb). Temperature-dependent thermodynamic properties of (Co,Ni)3(Al,Mo,Nb) can be described satisfactorily using the Debye–Grüneisen approach, including heat capacity, entropy, enthalpy, and linear thermal expansion coefficient. Predicted heat capacity, entropy, and linear thermal expansion coefficient of (Co,Ni)3(Al,Mo,Nb) show significant change as a function of temperature. Furthermore the obtained data can be used in the modeling of thermodynamic and mechanical properties of Co-based alloys to enable the design of high temperature alloys. I. INTRODUCTION
Ni-based superalloys cannot satisfy the increasing demand for materials with higher-temperature capabilities. Instead, Co-based superalloys display superior hot corrosion resistance at high temperatures compared to
Contributing Editor: Susan B. Sinnott a) Address all correspondence to this author. e-mail: [email protected] DOI: 10.1557/jmr.2017.8
Ni-based alloys.1 However, the traditional Co-based superalloys strengthened by carbide precipitates have not been widely used because they exhibit a lower strength at high temperatures with respect to Ni-based alloys strengthened by the formation of c9 Ni3(Al,Ta) phase.2 So far, the c9 phase has not been applied in Co-based commercial alloys. Interest in Co-based alloys has been fueled because of the discovery of the L12
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