First principles investigation of zinc-induced embrittlement in an aluminum grain boundary
First principles investigation of zinc-induced embrittlement in an aluminum grain boundary
复制标题
DOI：
10.1016/j.actamat.2011.06.028
复制
发表时间：
2011-09
期刊：
影响因子：
9.4
通讯作者：
Sheng-jun Zhang;O. Kontsevoi;Arthur J. Freeman;Gregory B. Olson
中科院分区：
文献类型：
--
作者：
Sheng-jun Zhang;O. Kontsevoi;Arthur J. Freeman;Gregory B. Olson
铝锌合金具有广泛的结构应用，但其对晶间应力腐蚀开裂的敏感性限制了其更广泛的应用。采用第一性原理计算方法，采用Rice-Wang热力学模型和从头算拉伸实验方法，研究了Zn对∑5（012）[100] Al晶界的影响.确定了Zn在Al晶界上沿着的最有利偏聚位置、Zn在Al晶界上的偏聚能、Zn在Al晶界上的可能断裂路径及相应的断裂能。我们确定Zn具有从Al块体到不对称晶界位置的偏聚的大驱动力（-0.19eVatom-1），并且其偏聚略微降低晶界强度。不寻常的是，偏析较大的原子尺寸Zn导致晶界收缩。通过精确计算，证实锌是一种弱脆化剂，其效力为+0.05eVatom 1。弛豫原子结构、电子结构和成键特征的分析表明，铝锌键在晶界和自由表面都具有金属性。这项工作提供了一个基本的定量的理解，锌引起的晶界脆化在铝合金的电子水平上，并建立了锌偏析是铝合金应力腐蚀开裂的因素之一。
Aluminum–zinc alloys have an extensive range of structural applications, but their susceptibility to intergranular stress corrosion cracking limits their wider use. In the present work the influence of zinc on a ∑5(012)[100] aluminum grain boundary was investigated by means of first principles calculations with the full potential linearized augmented plane wave method using two approaches: (i) within the framework of the Rice–Wang thermodynamic model; (ii) by the ab initio tensile test method. We determined the most energetically favorable segregation site of Zn along the Al grain boundary, its segregation energy from the Al grain boundary, the possible fracture paths of the grain boundary with Zn and the corresponding fracture energies. We established that Zn has a large driving force (−0.19eVatom−1) for segregation from the Al bulk to the asymmetrical grain boundary site, and its segregation reduces the grain boundary strength slightly. Unusually, segregation of larger atomic size Zn leads to grain boundary contraction. Through precise calculations it was confirmed that zinc is a weak embrittler with a potency of +0.05eVatom−1. Analysis in terms of the relaxed atomic and electronic structures and bonding characters showed that aluminum–zinc bonds have a metallic character in both grain boundary and free surface environments. This work provides a fundamental quantitative understanding of Zn-induced grain boundary embrittlement in Al alloys on the electronic level and establishes that Zn segregation is one of the factors contributing to stress corrosion cracking in Al alloys.