Abstract: Valence electron structure model of matrix and precipitates of Fe-Cu binary alloys are established by using empirical electron theory (EET) of solids and molecules, to reveals the Fe-Cu alloy strengthening mechanism from the electronic level. Theoretical results show that the Cu and Fe atoms form by chemical bonds in alloy, the covalent electron pairs of the strongest and the second strong bond of the metastable B2-like structure phase, which formed in the aging peak, is far stronger than that of α-Fe matrix cell, and the bond binding energy of precipitates is higher than the matrix as well. The strong Fe-Cu bonds arranged regularly, increases the covalent electron pairs of Fe-Cu strongest bond, and stabilize total bond of the alloy. At the same time, high bond energy Fe-Cu precipitates increases the resistance of dislocation motion, and strengthen the alloy. There is a good agreement between the EET theory analysis and experimental results for Fe-Cu precipitation hardening, so the reliability of the method is validated.

Key words: Empirical electron theory, Fe-Cu alloy, Strengthening, Valence electron structure