COMPRESSIVE CREEP-BEHAVIOR OF SPRAY-FORMED GAMMA-TITANIUM ALUMINIDE

The creep behavior of spray-formed gamma-TiAl with a fine, equiaxed fu lly lamellar (FL) microstructure was studied in a temperature-stress r egime of 780 degrees C to 850 degrees C and 180 to 320 MPa. An apparen t stress exponent of 4.3 and an activation energy of 342 kJ/mol were o bserved in the high-temperature high-stress regime. Compared with the FL gamma-TiAl which was obtained through conventional casting + heat t reatment processes, the spray-formed gamma-TiAl exhibited higher creep resistance. The higher creep resistance observed in the present study was discussed in light of the interstitial level, the chemical compos ition the grain size, and the interlocking Of lamellae at the grain bo undary, which in turn maybe a function of interlamellar spacing and th e step height of the serrated grain boundaries. It was suggested that the small interlamellar spacing and possibly larger step height may co ntribute to the higher creep resistance observed in the present study.