Effect of B on the superplasticity of Fe-6.6Mn-2.0Al alloy

The influence of B on the superplasticity of Fe-6.6Mn-2.0Al alloy was investigated by means of high-temperature tensile testing at temperatures ranging from 620 degrees C to 880 degrees C with initial strain rates of 1 x 10(-3) s(-1) and 1 x 10(-4) s(-1). Since the high-temperature deformation mechanism changed below and above similar to 750 degrees C, in-depth analyses were carried out using tensile specimens tested at 650 degrees C and 800 degrees C. The addition of B increased peak stress and apparent activation energy (Q(a)), but decreased or maintained strain rate sensitivity (m) value, average grain size (AGS) and gamma fraction, regardless of tensile temperature and initial strain rate. These results are related to the segregation of B atoms at prior gamma grain boundaries and alpha/gamma phase boundaries. When deformed at 650 degrees C, dominant deformation mechanisms of alpha and gamma phases were dislocation slip and GBS, respectively. Elongation decreased by the addition of B due to the less fraction of fine gamma grains undergoing GBS. When tensile temperature was 800 degrees C, both alpha and gamma grains underwent GBS and elongation increased by the addition of B. The higher elongation of the B-added alloy was most likely due to the finer grains resulting from the suppressed dynamic grain growth. Meanwhile, the addition of B did not provoke the self-healing effect due to the small amount of B and short deformation time.

Automated summary

The influence of B on the superplasticity of Fe-6.6Mn-2.0Al alloy was studied using high-temperature tensile testing. The addition of B increased peak stress and apparent activation energy, while decreasing strain rate sensitivity, affecting grain size and phase fraction. The increase in elongation with B addition may be attributed to the finer grains achieved by suppressing dynamic grain growth.