摘要
The nucleation properties and stability of the ordered precipitates in Al-Sc-Er alloy were extensively studied by first-principles calculation.The calculated substitutional formation energy reveals that the dissolved Sc or Er in the Al matrix is very favorable to substitute the X sublattice site in L1_(2)-Al_(3)X(X=Sc/Er).The calculated solubility curve demonstrates the significant contribution of vibrational entropy to nucleation.The interface energies for Al/Al_(3)Sc,Al/Al_(3)Er and Al_(3)Sc/Al_(3)Er were calculated in the three directions of[100],[110]and[111],and we find that the interface structure in(100)plane is the most desirable,and the interface energy of Al/Al_(3)Er is the largest.Regardless of temperature and Sc/Er ratio,the L1_(2)-Al_(3)Sc_xEr_(1-x)precipitation phase mainly forms as the core-shell structure with Al3 Er as the core and Al_(3)Sc as the shell due to lower nucleation energy.The core-shell structure behaves higher stability once the particle radius is greater than 1 nm.Furthermore,the thermodynamic driving force for the segregating of Si or Zr in Al-Sc-Er alloy should accelerate the precipitation kinetics,where Si partitions occur preferentially to the Al_(3)Er and Zr partitions preferentially to the Al matrix.Overall,these theoretical results can offer solid explanations to the available experimental results.
基金
Project supported by the National Key Research and Development Program of China(2018YFB1106302)
the National Natural Science Foundation of China(51821001)
the Shanghai Jiao Tong University(15X100040018)
the Anhui Province Engineering Research Center of Aluminum Matrix Composites(2017WAMC002)。
