Surface oxide debonding in field assisted powder sintering

Field activated sintering techniques (FAST) have been applied to two high-temperature powder materials: tungsten and NiAl. High and atomic resolution electron microscopy (HREM/ARM) of tungsten powder sintered via FAST showed essentially clean boundaries. Analytical transmission electron microscopy (TEM) of FAST sintered NiAl also showed boundaries free of surface oxide layer(s). However, small alumina precipitates were found at and near prior particle (grain) boundaries. The boundary cleaning and precipitation phenomena are manifestations of an applied pulsed electric field.