Ag对Al-Cu-Mg合金固溶体价电子结构及时效惯序的影响

Valence Electron Structure and Aging Sequence of Solid Solution in Al-Cu-Mg Alloy with Addition of Ag

基于EET理论(empirical electron theory of solids and molecules),计算了Al-Cu-Mg-Ag合金α-Al,α-Al-Mg,α-Al-Ag,α-Al-Cu固溶体和时效初期α-Al-Mg-Ag,α-Al-Mg-Cu固溶体的价电子结构,用最强共价键的共价电子数n1和结构单元总成键能力F分析了固溶体结构的稳定性,研究了Ag在基体{111}面上偏聚对Mg,Cu偏聚行为和合金时效析出惯序的影响。研究表明:α-Al-Cu,α-Al-Ag和α-Al-Mg的总成键能力分别比α-Al的小35.40%,15.32%和6.24%,α-Al-Cu,α-Al-Ag和α-Al-Mg的结构稳定性均小于α-Al的结构稳定性。α-Al-Ag和α-Al-Mg最强共价键的n1值分别比α-Al的大31.30%和21.43%,而α-Al-Cu最强共价键的n1值比α-Al的小0.14%,Cu在{111}面集聚没有驱动力。随着时效的进行,时效初期形成的α-Al-Mg-Ag的最强键、次强键的键合力和总成键能力逐渐增大,结构越来越稳定;而α-Al-Mg-Cu各共价键的键合力和总成键能力逐渐减小,结构越来越不稳定,易于发生改组重构。Cu原子因Mg,Ag原子而在{111}面上集聚,为Ω相的形成提供了形核基础;Mg,Ag原子不直接参与Ω相的形核,但为其形核提供了触媒剂。{111}面上Ag,Mg原子的集聚减少了{001}面上的Cu和Mg原子,抑制了θ′和S相的析出。

Based on the empirical electron theory of solids and molecules,the valence electron structures of solid solution ofα-Al,α-Al-Mg,α-Al-Ag,andα-Al-Cu in Al-Cu-Mg alloy were calculated,and the valence electron structures of solid solution ofα-Al-Mg-Ag andα-Al-Mg-Cu in Al-Cu-Mg alloy at the early aging stage were also calculated.The stability of these solid solution structures was analyzed using n1,the covalent electron number of the strongest covalent bond,and F,the total banding ability of structural unit,then the effect of Ag segregation on the{111}αplane to the segregation behavior of Mg and Cu atoms and the alloy aging sequence was studied.The results showed that the total banding abilities ofα-Al-Cu,α-Al-Ag,andα-Al-Mg were 35.40%,15.32%and 6.24%smaller than that ofα-Al,respectively.So their structural stability was lower that ofα-Al.The n1 values of the strongest covalent bonds ofα-AlAg andα-Al-Mg were 31.30%and 21.43%bigger andα-Al-Cu was 0.14%smaller than that ofα-Al,respectively,therefore Cu segregation on the{111}αplane had no driving force.With the aging process,the bonding force of the strongest and the second strongest bonds and the total banding ability of Al-Cu-Mg-Ag formed in the early aging period gradually increased,and its structure became more and more stable.However,the bonding force of covalent bonds and the total banding ability ofα-Al-Mg-Cu gradually decreased,and its structure became more and more unstable,which was prone to reorganization and reconstruction.Because of Mg and Ag atoms,Cu atom gathered on{111}αplane,provided nucleation basis for the formation ofΩphase.Mg and Ag atoms did not directly participate in the nucleation ofΩphase,but providedΩcatalyst for its nucleation.The segregation of Ag and Mg atoms on the{111}αplane reduced the Cu and Mg atoms on{001}αplane,and inhibited the precipitation ofθ′and S phases.