The focused ion beam (FIB) miller has been widely accepted as a powerful tool in the semiconductor industry. However, it is now finding applications in more general materials science applications. The high resolution, energetic gallium ion beam can rapidly and precisely section materials to reveal their internal structure; one particularly valuable application being the preparation of thin foils for TEM examination, especially from heterogenous materials.

To date, TEM sample preparation using FIBs has concentrated on semiconductor cross-sections [1], powders [2], and surface treated materials, e.g. galvanized steels [3]. However, thin foils of grossly heterogeneous materials, such as metal-matrix composites, are also difficult to prepare using conventional methods and are therefore well suited to sectioning using the FIB. In this study, thin foils were prepared from two composite materials: a 7075 aluminium alloy containing a 20% volume fraction of SiC particles and a FeAl alloy containing a 60% volume fraction of WC particles.