The definitive indexing of phases with similar lattice parameters based solely on their Kikuchi patterns during electron back-scattering diffraction (EBSD) is an ongoing concern in the microanalysis of composite materials. A classic example is that of aluminium (Al, a ≈ 4.05 Å) and copper (Cu, a ≈ 3.62 Å) composites; where the individual phases are chemically distinct but the difference in their lattice parameters (a) is less than 12%. In this study we demonstrate that the acquisition of energy dispersive X-ray spectroscopy (EDS) information before proceeding with the indexing of a Kikuchi pattern successfully identifies individual phases within (sub)grain interiors in an 8 pass accumulative roll bonded (ARB) Al-Cu composite material. However, the EDS-EBSD data acquisition process is unable to differentiate the phases at (sub)grain boundary areas. Monte-Carlo simulations show that this error is attributed to differences in the size of the interaction volume and the apparent centre-displaced-from-the-origin of the received X-ray and back-scatter signals at high sample tilt. This finding was confirmed by re-acquiring EDS and EBSD data at lower accelerating voltage.