Thermomechanical processing and mechanical characteristics of particle-strengthened iron aluminide-based alloys

By the introduction of a fine dispersion of stable particles, a new family of chromium-containing iron aluminide-based alloys, has been developed. These alloys exhibited modified recrystallisation kinetics, creep and tensile strengths and welding characteristics. The existence of a second phase dispersion reduced the tendency for localised deformation. Uniform deformation was promoted and ductility improved. Dispersoid additions improved microstructural stability and the recrystallisation rate was retarded by more than a factor of two. The room temperature tensile ductility as well as the tensile strength of the particle-modified alloy were increased. Furthermore, the onset of micro void coalescence occurred at lower temperatures. At 700 C both alloys exhibited similar strain rate sensitivities. Charpy impact toughness tests showed that the ductile to brittle transition temperature for the thermomechanically treated alloys was approximately 250 C and about 50 C higher for the particle-containing alloy. This apparent decrease in impact toughness was attributed to large inclusions observed in the cast microstructure. (orig.)