DEFORMATION AND FRACTURE CHARACTERISTICS IN TIAL AT ROOM-TEMPERATURE AND 800-DEGREES-C

The characteristics of deformation and fracture at room temperature an d 800 degrees C of a binary (gamma-alpha(2))-Ti-48 at.%Al intermetalli c with a duplex microstructure have been identified by scanning and tr ansmission electron microscopy (SEM and TEM). A change in the predomin ant fracture mode from transgranular at room temperature to intergranu lar at 800 degrees C has been observed which coincided with profoundly different plastic behavior of the alpha(2)-phase. The alpha(2)-lamell ae exhibited only localized planar slip of [a] dislocations during roo m temperature deformation, whereas at 800 degrees C [a] dislocations a re activated more generally, and in addition motion of [c]-component d islocations has been implied. The gamma-TiAl phase deformed by ordered twinning and slip of both ordinary and superdislocations during loadi ng at both temperatures. (C) 1997 Elsevier Science B.V.