TUNGSTEN SEGREGATION IN ALPHA(2)+GAMMA TITANIUM ALUMINIDES

Atom probe field ion microscopy investigations of alpha(2)+gamma Ti-47 %Al-2%Cr-1.8%Nb doped with 0.15% B and 0.2% W indicate that the tungst en segregates to both gamma/gamma and alpha(2)/gamma interfaces. The i nterfacial coverage of tungsten at a specific gamma/gamma interface wa s estimated to be 2.3% which yields a segregation enhancement factor o f similar to 14. Initial results give no appreciable evidence of boron segregation to interphase interfaces. Interfacial segregation of tung sten supports the previous observation that tungsten additions stabili ze the at lamellae against dissolution during aging. (C) 1997 Elsevier Science Limited.