Phase equilibria, martensitic transformations and deformation behaviors of the subsystem of Cantor alloy−low-cost Fe-Mn-Cr alloys

Abstract

Investigations of the Fe-Mn-Cr system are not only significant for developing Cantor alloy but also valuable for designing low-cost, high-strength steel. In this study, we experimentally determined the phase equilibria of this system for establishing the thermodynamic database. Additionally, the influences of Mn on both the phase transformation and deformation behaviors of the Fe-Mn-Cr alloys were studied. Fe was found to solute into σHT phase with a large solubility at 1323 and 1473 K. A (βMn) single-phase region was initially discovered at 1473 K. The (βMn)+(γFe) and σHT+(Cr) two-phase regions were respectively found to be very narrow. During tensile testing, the transformation-induced-plasticity (TRIP)- type was discovered to change from ε→α′ to (γFe)→ε when Mn increased from 20 to 30 at. %. The stacking fault energy (SFE) was measured to be 8.1 mJ·m−2 for 30Mn alloy. Contrarily, the stacking fault did not seem to occur during the tensile testing of 40Mn alloy. The 0.2 % proof stresses for Fe(90-x)MnxCr10 alloys were measured to be 633 (10Mn), 345 (20Mn), 166 (30Mn), and 188 MPa (40Mn), respectively. The TRIP effect was discovered in the tensile testing of 30Mn alloy, which exhibited an ultimate tensile strength of 755 MPa and a uniform elongation of 38.7 %. It is to be noted that no recovery of work-hardening rate occurred during the tensile testing of 40Mn alloy. The investigated phase equilibria and deformation behaviors of the Fe-Mn-Cr alloys are believed to accelerate the design of Cantor-alloy-related materials and Fe-Mn-Cr-based high-strength steel.