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

A detailed description is given of the microstructure of the top layer of T i-6Al-4V with SiC particles embedded with a high-power Nd:Yag laser system. Scanning electron microscopy (SEM), as well as conventional, analytical an d high-resolution transmission electron microscopy (TEM) were used. An exis ting controversy about the presence or absence of Ti3SiC2 in the reactive S iC/Ti systems is clarified and the first observations of Ti5Si3 precipitati on on stacking faults in Si supersaturated TiC are reported. The Si release d during the reaction SiC + Ti --> TiC + Si results in the formation of Ti5 Si3. If in the reaction layer regions in between the TIC grains become encl osed, the rejected Si content increases locally and Ti3SiC2 plates with dom inant (0001) facets nucleate. In the TiC grains particularly of the cellula r 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 Ti 5Si3 precipitates are present. (C) 1999 Acta Metallurgica Inc. Published by Elsevier Science Ltd. All rights reserved.