Hot deformation and processing maps of an Fe3Al intermetallic alloy

The deformation behavior of an Fe-28Al-5Cr-0.08Zr-0.04B (at.%) intermetallic alloy under hot compression conditions was characterized in the temperature range of 600 1100 deg C and strain rate range of 0.001-100 s(-1). Processing maps were calculated to evaluate the efficiency of the hot working and to recognize the instability regions of the flow behavior. The investigated alloy possesses the optimum hot-working conditions at 1100 deg C and 0.001 s(-1), since the material undergoes dynamic recrystallization to produce a fine-grained structure with a high fraction of high-angle boundaries (~70%). At lower temperature the material exhibited "large grained superplasticity" with a peak efficiency of ~60% at 1000 deg C and 0.001 s(-1). These parameters are the optimum ones for superplastic working of that alloy. The occurrence of large grained superplasticity is attributed to the formation of a subgrain structure within the large original grains and higher strain-rate sensitivity. The material also exhibits flow instabilities due to flow localization at lower temperatures ( < 700 deg C) and higher strain rates ( > 0.1 s(-1)).