Analysis On The Interface Valence Electron Structure In Al-Li-Cu Alloy And Its Effects On Properties Of Strengthening

The valence electron structures of the interface between precipitations and matrix in Al-Li-Cu based alloy are analyzed according to the Empirical Electronic Theory in solid and molecules (EET). The following aspects are included in this thesis:1 .The model of ordered strengthening is established and strengthening mechanicms in Al-Li based alloys are investigated on the valence electron structure level.2. Precipitation sequence in the Al-Cu alloys is analyzed on the valence electron structure level.3. The interface valence electron structures of the precipitations such as a -Al/T1(Al2CuLi) of Al-Li-Cu based alloy are calculated.The results show that:APB forms because of the movement of dislocation in Al-Li alloy. Theplanar defect energy of APB is so high that it hinders the movement of the dislocation, Consequently, the strength of the alloy promotes.The similarities and differences in the structure of the matrix and precipitation are qualitatively analyzed, and the amounts of valence electron are calculated according to the EET. The results show when " phases precipitates, the redistributions of valence electrons change least, ' next, lastly. Consequently," precipitate firstly, ' secondly, lastly in the aging process.The interface energy between the matrix and the precipitates in Al-Li-Cu base alloy is calculated. The results show interface energy of (Al3Li)/a-Al is so little that tiny phase distributes homogeneously in the matrix, playing a role in dispersion strengthening. Likewise, in Al-Cu base alloy, the tiny " played a role in dispersion strengthening because the interface energy of "/a-A\ is least, and that of /a-Al is highest, so 9 easily becomes coarse, the strength of the alloy decreases. The interface energy of T1/a-Al is between "/a-Al and /a-Al, so T1 can precipitate directly in the aging when conditions allow.