First-Principles Investigation of the Diffusion of TM and the Nucleation and Growth of L12 Al3TM Particles in Al Alloys

Abstract

The key parameters of growth and nucleation of Al3TM particles (TM = Sc-Zn, Y-Cd and Hf-Hg) have been calculated using the combination of the first principles calculations with the quasi-harmonic approximation (QHA). Herein, the diffusion rate Ds of TM elements in Al is calculated using the diffusion activation energy Q, and the results show that the Ds of all impurity atoms increases logarithmically with the increase in temperature. With the increase in atomic number of TM, the Ds of 3–5d TM elements decreases linearly from Sc, Y and Hf to Mn, Ru and Ir, and then increases to Zn, Ag and Au, respectively. The interface energy γα/β, strain energy ΔEcs, chemical formation energy variation ΔGV and surface energy Esurave were further computed from the based interface and slab models, respectively. It was found that, with the increase in the atomic number of TM, the interface energies γα/β of Al/Al3TM (TM = (Sc-Zn, Y-Cd)) decreased from Sc and Y to Mn and Tc and then increased to Zn and Cd, respectively (except for the (001) plane of Al/Al3(Fe-Co), the (111) plane of Al/Al3Pd and the (110) and (111) planes of Al/Al3Cd). The strain energies ΔEcs of Al/Al3TM (TM = (Sc-Zn)) increased at first, and then decreased for all cycles. The chemical formation energy ΔGV of all Al3TM changed slightly in the temperature range of 0~1000 K, except that the ΔGV of Al3Sc, Al3Cu, Al3(Y-Zr), Al3Cd, Al3Hf and Al3Hg increased nonlinearly. With the increase in atomic number at both 300 and 600 K, the ΔGV of 3–5d TM elements increased from Sc, Y and Hf to Mn, Tc and Re at first, and then decreased to Co, Rh and Ir, respectively, and slightly changes at the end. With the increase in atomic number of TM, the variation trends of the surface energies of Al3TM intermetallic compounds present similar changes for all cycles, and the (111) surface always has the lowest values.

Microstructure and Properties in Metals and Alloys

“…T. Hu et al [25] describe the diffusion of TM and the nucleation and growth of particles in Al alloys based on first principles.…”

Kinetics and Thermodynamics of the Phase Transformation in the Nanocrystalline Substance—Gas Phase System

“…There is an extensive body of literature on diffusion processes in various types of macroscopic, coarsely crystalline structures [1][2][3][4][5][6][7].…”

First-Principles Study of Atomic Diffusion by Vacancy Defect of the L12-Al3M (M = Sc, Zr, Er, Y) Phase

“…Although experimental methods were difficult to investigate atomic diffusion in intermetallic compounds [ 19 , 20 ], first-principles calculations can provide new insights into the microscopic mechanisms of atomic diffusion [ 18 , 20 ]. First-principles calculations by Fan [ 21 , 22 ] showed that with the increase of the atomic number, the diffusion rate of rare-earth elements increased from Sc to Y, La, and then decreased to Lu. Shi et al [ 23 ] investigated the atomic diffusion of pure and transition-element (TM)-doped L1 2 -Al 3 Sc based on first principles and found that under a strong Al-rich condition, the V Sc defect obtained low formation energy and the NNJ mechanism mediated by V Al was most favorable for Sc atomic diffusion.…”