In-Situ Synthesis of Alumina Reinforced (Fe,Cr)3Al Intermetallic Matrix Nanocomposite

In this study, a mixture of chromium oxide, elemental iron, and aluminum powders was subjected to high energy ball milling to produce Al2O3 reinforced (Fe,Cr)(3)Al matrix nanocomposite. The structural changes of powder particles during milling were investigated by X-ray diffractometry. Cross-sectional microstructure of powder particles after different milling times was observed by scanning electron microscopy using back scatter mode. The change in morphology of powder particles was followed by scanning electron microscopy observations. The transmission electron microscopy was used to confirm the development of nano-sized structure in the final product. The changes in phase composition, structure and morphology of powder particles suggested that during milling, Al gradually reacts with Cr2O3 leading to the formation of metallic Cr and Al2O3 phases and concurrently, the reduced Cr and remaining Al diffuse into the Fe lattice and as a result, a Fe(Al,Cr) solid solution forms. This structure was transformed to (Fe,Cr)(3)Al intermetallic compound at longer milling times.