FIB‐SEM investigation of trapped intermetallic particles in anodic oxide films on AA1050 aluminium

Abstract

PurposeThe purpose of this investigation is to understand the structure of trapped intermetallics particles and localized composition changes in the anodized anodic oxide film on AA1050 aluminium substrates.Design/methodology/approachThe morphology and composition of Fe‐containing intermetallic particles incorporated into the anodic oxide films on industrially pure aluminium (AA1050, 99.5 per cent) has been investigated. AA1050 aluminium was anodized in a 100 ml/l sulphuric acid bath with an applied voltage of 14 V at 20°C ±2°C for 10 or 120 min. The anodic film subsequently was analyzed using focused ion beam‐scanning electron microscopy (FIB‐SEM), SEM, and EDX.FindingsThe intermetallic particles in the substrate material consisted of Fe or both Fe and Si with two different structures: irregular and round shaped. FIB‐SEM cross‐sectioned images revealed that the irregular‐shaped particles were embedded in the anodic oxide film as a thin strip structure and located near the top surface of the film, whereas the round‐shaped particles were trapped in the film with a spherical structure, but partially dissolved and were located throughout the thickness of the anodic film. The Fe/Si ratio of the intermetallic particles decreased after anodizing.Originality/valueThis paper shows that dual beam FIB‐SEM seems to be an easy, less time consuming and useful method to characterize the cross‐sectioned intermetallic particles incorporated in anodic film on aluminium.