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 °C to 880 °C with initial strain rates of 1 × 10−3 s−1 and 1 × 10−4 s−1. Since the high-temperature deformation mechanism changed below and above ~750 °C, in-depth analyses were carried out using tensile specimens tested at 650 °C and 800 °C. The addition of B increased peak stress and apparent activation energy (Qa), but decreased or maintained strain rate sensitivity (m) value, average grain size (AGS) and γ fraction, regardless of tensile temperature and initial strain rate. These results are related to the segregation of B atoms at prior γ grain boundaries and α/γ phase boundaries. When deformed at 650 °C, dominant deformation mechanisms of α and γ phases were dislocation slip and GBS, respectively. Elongation decreased by the addition of B due to the less fraction of fine γ grains undergoing GBS. When tensile temperature was 800 °C, both α and γ 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.
Bibliographical noteFunding Information:
This research was supported by the Basic Science Research Program through the National Research Foundation of Korea ( NRF ) funded by the Ministry of Education (Grant number: NRF- 2018R1D1A1A09083753 ) and the Technology Innovation Program (Alchemist Project, 20012196, Al-based supercritical materials discovery) funded by the Ministry of Trade, Industry & Energy, Korea.
© 2021 Elsevier B.V.
All Science Journal Classification (ASJC) codes
- Materials Science(all)
- Condensed Matter Physics
- Mechanics of Materials
- Mechanical Engineering