Superplasticity in large-grained Fe3Al alloys

The superplasticity behavior of Fe-28Al, Fe-28Al-2Ti and Fe-28Al-4Ti (all compositions reported in this paper are in atomic percent) alloys has been investigated by tensile testing, optical microscopy and transmission electron microscopy. Tensile tests were performed at 700-900 degrees C under a strain rate range of about 10(-5)-10(-2)/s. The maximum strain rate sensitivity index m was found to be 0 . 5 and the largest elongation reached 620%. The flow activation energy was measured to be 263 kJ/mol for Fe-28Al and 191 KJ/mol for Fe-28Al-2Ti, which is much lower than the creep activation energy generally observed in Fe3Al alloys. After deformation, the grain size became much finer; from about 100 mu m to 20-30 mu m. As combined with TEM observations, we suggested that a continuous recrystallization process took place and superplasticity may arise from this process. Copyright (C) 1996 Elsevier Science Ltd