Tensile deformation behavior analysis of low density Fe-18Mn-10Al-xC steels

Three low density Fe-18Mn-10Al-xC steels containing 0.5, 0.8 and 1.2 C (wt%) were utilized to investigate the differences in microstructures and their influence on mechanical behaviors during plastic deformation. The 0.5C steel had a duplex ferritic-austenitic structure and the fraction of austenite was similar to 59.2%, while the fraction of austenite was similar to 84.8% for the 0.8C steel and some ordered phases existed in both ferrite and austenite. In contrast, a fully austenitic microstructure with some kappa carbides was achieved in the 1.2C steel. Due to the existence of the ordered phases by the addition of C from 0.5% to 0.8%, the 0.8C steel exhibited a highest tensile strength of similar to 979 MPa, and a moderate strain hardening capacity. The 1.2C steel revealed a superior combination of strength and ductility (ultimate tensile strength of 946.7 MPa and elongation to failure of 56%), with a much more pronounced strain hardening than the other two steels. The differential Crussard-Jaoul (C-J) analysis demonstrated a two-stage strain hardening behavior in both 0.5C and 0.8C steels, while a three-stage one in the 1.2C steel. This difference in strain hardening behavior was further understood in terms of microstructural analysis at the different stages of plastic deformation. (C) 2015 Elsevier B.V. All rights reserved.