Al-Zn-Mg-Cu超高强铝合金晶界偏聚与腐蚀机制研究

Grain-Boundary Segregation and Corrosion Mechanism of Al-Zn-Mg-Cu Ultra High Strength Aluminum Alloys

摘要:

采用自编软件建立Al-Zn-Mg-Cu合金中α-Al、η(MgZn2)相及晶界含η相的α-Al大角度晶界原子集团模型。用递归法计算合金中Zn、Mg、Cu的环境敏感镶嵌能、原子相互作用能，α-Al和η相结合能、费米能级等电子参数。并依据电子参数分析合金的腐蚀特性。结果显示：合金元素Mg、Cu容易在晶界偏析，Mg、Zn形成η相原子集团。因Mg在晶界偏析，晶界析出的η相较为粗大，晶内形成的η相比较细小。计算还表明：η相的费米能级最高，在腐蚀过程中作为阳极优先溶解。合金元素Zn具有增大晶界、晶内电位差的作用，降低合金的抗腐蚀性。Cu能减小晶界与晶内费米能级差，降低晶界与晶内的电位差，具有减缓合金腐蚀的作用

Abstract:

The atomic cluster models of α-Al, η phase and large angle grain boundary of α-Al with η phase in Al-Zn-Mg-Cu alloys have been founded by a computer program. The environment-sensitive embedding energy, and the atom action energy of Zn, Mg, Cu and the atom binding energy, the fermi energy of α-Al and/or η phase have been calculated by a recursion method. The corrosion character of Al-Zn-Mg-Cu alloys has been studied according to the calculated electronic parameter. The results show that Mg and Zn elements are easy to segregate on grain boundaries, and to form η phase. The η phase on grain boundary are large then that in grain due to the segregation of Mg in the grain boundary. The calculated results indicate that the fermi energy of η phase is the highest, will be decomposed firstly in the corrosion as an anode. The alloy element Zn has the function to increase the electrode potential difference between grain boundary and grains, to deteriorate the corrosion character of alloys. The alloy element Cu can reduce the difference of Fermi energy and the potential difference between grain and grain boundary, so as to slow down the corrosion process