Superplastic behavior of a kappa carbide material (Fe₃AlC_x)

Fine-grained kappa carbide (Fe₃AlC_x) materials, containing 12.5 and 14% Al, and 3.5% C, were prepared by powder processing and hipping procedures. The creep behavior of the kappa materials was shown to be identical to that observed in superplastic iron carbide, and was shown to follow a grain boundary–diffusioncontrolled grain boundary sliding relation. The tensile fracture strains in kappa, however, were shown to be considerably less than in iron carbide with a maximum elongation of 92% noted. This difference is attributed to either a low stress intensity factor or to contamination of the powder surface in the kappa material. The compression creep strength, at a given strain rate, was shown to be about two times higher than the tension creep strength.