PROPERTIES AND APPLICATIONS OF INTERMETAL LIC B2-FEAL ALLOYS

Ordered FeAl intermetallic alloys are attractive materials for medium and high temperature industrial applications but their use has been re stricted until now by their room temperature brittleness and their poo r creep resistance. Powder metallurgy (Pin?) techniques such as gas at omization and mechanical milling have been used to develop FeAl alloys with enhanced ductility and strength at both low and high temperature s. The improvement method combines ductilization by grain boundary str engthening, grain size reduction and oxide dispersion strengthening. T hese materials named FeA140 Grade 3 have been characterized and tested in the form of extruded bars. Microstructure and texture of as-extrud ed and heat treated samples have been studied by TEM and X-rap diffrac tion. Grains are 0,5 mu m in size, resistant to recrystallization up t o 1100 degrees C and exhibit a strong [110] wire texture parallel to t he extrusion axis. The Y2O3 dispersoids (20-30 nm in size) are cylindr ical in shape and partially coherent with the matrix. The yield streng th and the elongation of such alloys can reach 900 Mpa and 6,4% in air . Physical and mechanical properties of these materials are compared t o some conventional engineering alloys in order to discuss the conceiv able applications in aeronautical and automotive industries. Due to th e high specific stiffness and strength of FeA140 Grade 3 alloys, promi sing applications are the substitutions of steels and superalloys for the fabrication of moving parts in thermal and aeronautical engines, a nd especially parts submitted to critical vibrating modes.