Color etching as a tool for phase identification in an AA1100–25 vol.% B4C metal matrix composite

Abstract

A color-etching methodology was applied to an AA1100–25 vol.% B4C composite to enhance phase identification under optical microscopy. A solution of 50% (v/v) phosphoric acid in deionized water was used at − 5 °C under a constant current density of 0.02 A cm−2. As a result, the aluminum matrix appeared pink, the B4C particles dark brown, TiB2 interfacial layers formed distinct contours around the B4C reinforcement, and the Si-rich inclusions exhibited a bright blue hue. These contrasts made the interfaces between the B4C particles and the aluminum matrix clearly distinguishable. Complementary SEM and EDS analyses confirmed the presence of TiB2 at the Al/B4C interfaces and Si-rich phases within the matrix. The proposed methodology provides a rapid and reliable means of identifying secondary phases and interfacial layers in Al–B4C composites.