Reaction layers around SiC particles in Ti: An electron microscopy study

A detailed description is given of the microstructure of the top layer of Ti-6Al-4V with SiC particles embedded with a high-power Nd:Yag laser system. Scanning electron microscopy (SEM), as well as conventional, analytical and high-resolution transmission electron microscopy (TEM) were used. An existing controversy about the presence or absence of Ti3SiC2 in the reactive SiC/Ti systems is clarified and the first observations of Ti5Si3 precipitation on stacking faults in Si supersaturated TiC are reported. The Si released during the reaction SiC + Ti --> TiC + Si results in the formation of Ti5Si3. If in the reaction layer regions in between the TIC grains become enclosed, the rejected Si content increases locally and Ti3SiC2 plates with dominant (0001) facets nucleate. In the TiC grains particularly of the cellular reaction layer, a high density of widely extending stacking faults of the order of 100 nm is observed and on these faults in many instances small Ti5Si3 precipitates are present. (C) 1999 Acta Metallurgica Inc. Published by Elsevier Science Ltd. All rights reserved.