Insights into the high magnetic field-induced austenite formation in medium manganese steel

Abstract

The mechanism of austenite formation in medium Mn steel tempered at 700 °C for 3 h without and with a 12 T magnetic field was investigated. The application of magnetic field results in lattice distortion of the martensite matrix, implying the presence of fewer interstitial carbon atoms embedded in the martensite matrix. The decreased interstitial carbon atoms are either free in the matrix or involved in the formation of nanoscale carbides, both of which prepare for the growth of carbides and the austenite formation. Meanwhile, doping of Mn enables the paramagnetic austenite to undergo a magneto-structural coupling transformation (i.e., paramagnetic γ-Fe transforms into weakly ferromagnetic γ-FeMn). The external field-induced change of the magnetic free energy emphasizes the probability for austenite formation, which agrees well with the experimental results.

Keywords

• High magnetic field
• Medium manganese steel
• Lattice distortion
• Austenite