MOBILE DISLOCATIONS AT THE ALPHA-2 GAMMA-PHASE BOUNDARIES IN INTERMETALLIC TIAL TI3AL-ALLOYS/

Ti3Al/TiAl interfaces of four titanium-aluminium alloys with and witho ut chromium additions were examined in detail by tilting experiments u sing conventional transmission electron microscopy (TEM). Careful adju stment of weak beam conditions showed that the TiAl- as well as the Ti 3Al- phase contain interfacial dislocations which accommodate the latt ice misfit between both phases. In the most ductile TiAl47Cr1Si0.2 all oy only one set of [110] interfacial dislocations in the TiAl phase wa s found. Most of them possess screw character and will leave the inter face during plastic deformation. Consequently, this alloy exhibits rem arkable ductility at room temperature.