J. Mater. Sci. Technol. ›› 2019, Vol. 35 ›› Issue (9): 2115-2120.DOI: 10.1016/j.jmst.2019.05.016

• Orginal Article • Previous Articles    

Interpolation and extrapolation with the CALPHAD method

Qun Luoa, Cong Zhaia, Dongke Sunb, Wei Chenc, Qian Lia*()   

  1. a State Key Laboratory of Advanced Special Steel & Shanghai Key Laboratory of Advanced Ferrometallurgy & School of Materials Science and Engineering, Shanghai University & Shanghai Institute of Materials Genome & Materials Genome Institute, Shanghai University, 333 Nanchen Road, Shanghai 200444, China
    b School of Mechanical Engineering, Southeast University, Nanjing 211189, China
    c Key Laboratory of Power Beam Processing, AVIC Manufacturing Technology Institute, China
  • Online:2019-09-20 Published:2019-07-26
  • Contact: Li Qian
  • About author:

    1 These authors contributed equally to this work.

Abstract:

It is widely reported that CALPHAD is an extrapolation method when the thermodynamic properties of a multicomponent system are approximated by its subsystems. In this work the meaning of the words extrapolation and interpolation is discussed in context of the CALPHAD method. When assessing the properties in binary and ternary systems, extrapolation method is indeed often used. However, after assessment, the Gibbs energies are in fact interpolated from the lower order systems into the higher order systems in the compositional space. The metastable melting temperatures of bcc and hcp in Re-W and the liquid miscibility gap in Mg-Zr system are predicted to illustrate the difference between interpolation and extrapolation.

Key words: CALPHAD, Interpolation, Extrapolation, Gibbs energy