Abstract: The inhibitory effect of the second phase on dislocation movement has long been deemed as a great contribution to the strengthening of alloys. We investigate the electronic behavior at the α-Al matrix/second phase interface to explore its inhibitory effect on dislocation movement. This work focuses on the difficulty in dislocation movement on the interface of α-Al/Al₃Sc, α-Al/θ'(Al₂Cu), and α-Al/T₁ (Al₂CuLi) of aluminum-lithium-scandium alloy based on detailed transmission electron microscopy investigation and electron transport calculation. The more drastic the electron transport between two atoms at the interface, the more intense the interaction between them, corresponding to the larger difficulty in breaking and forming bonds between them during the movement process of the extra half plane of dislocation on the interface. The calculated difference in density of valence electrons and differential charge density at α-Al/second phase interface reveals that Al₃Sc is characterized by the largest resistance to dislocation movement compared to θ'(Al₂Cu) and T₁ (Al₂CuLi). The large differential charge density between the interface of (1 0 0)_Al3Sc/(1 0 0)_Al demonstrates the strong bonds between α-Al and Al₃Sc and the large difficulty for the extra half plane of dislocation to form or break bonds during the movement process at α-Al/Al₃Sc interface. The dislocation pile-up indicates a discernible hindering effect of the α-Al/Al₃Sc interface on dislocation movement. The hindering effect presented by α-Al/Al₃Sc interface is favorable for the tensile strength.

Key words: Dislocations, Microstructural interface, Aluminum alloy, Electron transport, First-principles calculation