Al-Li合金时效初期的价键分析

来源期刊：中国有色金属学报2005年第7期

论文作者：高英俊 黄创高 莫其逢 蓝志强 刘慧 韦银燕

文章页码：1069 - 1074

关键词：Al-Li合金; Al₃Li; 空位; 价电子结构; 力学性能

Key words：Al-Li alloy; Al₃Li; vacancy; covalence bond; mechanical properties

摘    要：运用固体经验电子理论(EET)， 对Al-Li合金时效初期的若干偏聚晶胞的价电子结构进行了计算。 计算结果表明： 不包含空位的偏聚晶胞的键络最强键为Al—Al键， 其中Al原子的共价半径较Li原子的共价半径要大； 而含空位的偏聚晶胞的最强键为Al—Li键， Al原子的共价半径要比Li原子的共价半径要小； 在空位存在的情况下， 由于Al原子与Li原子的电负性相差明显， 促使Al和Li原子结合， 倾向形成Al-Li短程序结构偏聚区， 这种含空位的短程序结构很可能就是δ′(Al₃Li)亚稳相的前兆结构和生长胚胎； 由于Al-Li-空位有序偏聚晶胞的Al—Li键络比基体键络要强许多， 因此， 淬火过程中合金生成的Al-Li-空位偏聚晶胞对合金过饱和固溶体起主要强化作用； 后续析出的δ′(Al₃Li)亚稳相键络各项异性显著， 键络强度明显提高； 由于Al₃Li与基体共格， 其大量均匀弥散析出起到提升基体整体键络强度， 同样对合金产生强化作用。

Abstract: The valence electron structures of the segregated cell of Al-Li alloy in earlier aging condition were calculated according to the empirical electron theory (EET) in solid. The results show: the strongest bond is the Al-Al bond in the segregated cell without containing vacancy, where the Al atomic covalence radius is greater than that of Li atom in the cell; while the strongest bond is the Al-Li bond in the segregated cell containing vacancy, and the Al atomic covalence radius in the cell is less than that of Li atom. Since the difference of electronagativity between the Al and Li atoms is obvious, it is inclined to formed the Al-Li segregated cell of short range order structure in the condition of vacancy present. The short range order structure containing vacancy is probably the embryo or precursor structure of the metastable phase δ′(Al₃Li). Because the strongest covalent bond in the Al-Li-vacancy segregated cell in alloy formed in quenching is the main strength reason for supersaturated solid solution of alloy. The bond net of succeeding precipitation of δ′(Al₃Li) has the picture of anisotropic Al-Al bonding and the bond intensity enhanced. Since the δ′(Al₃Li) is coherence with matrix, the bond net strength is enhanced by the precipitation of δ′(Al₃Li) and so strengthen the alloy.