Interstitial triggered grain boundary embrittlement of Al–X (X = H, N and O)

With the quick development of high-speed railway and the service of the series of CRH (China Rails High-speed) for almost a decade, one of the greatest challenges is the managements/maintenances of those trains in environmental conditions. It is critical to estimate the intergranular corrosion damage initiations and propagations, thus, to setup the relative database in order to support foundations for an interactive corrosion risk management. In this work, ∑301111¯1 coherent twin boundary (CTB) of FCC Al–X is utilized to reveal the interactions between interstitials (X = H, N and O) and CTB together with their embrittlement mechanism. The HCP-type fault layers within the CTB are same as those fault layers in growth fault, indicating the local FCC-HCP transformation at CTB and revealing the physical foundation for those criteria designing growth twins. The notable accumulation of bonding electrons of interstitial atoms occupying either T-site or O-site yields a dramatically reduction of Al–X and Al–Al bonding charge density and bonding strength, revealing the embrittlement mechanism of Al CTB.