Effects of Mn Content on Microstructure and Mechanical Properties of Fe-Mn Alloy

Effects of Mn content on microstructure and mechanical properties in Fe-Mn alloys containing various Mn ranging from 3% to 12% （mass%） have been studied by scanning electron microscopy（SEM）,transmission electron microscopy（TEM）,electron back scattered diffraction（EBSD）,tensile and Charpy impact tests.When Mn content is in the range of 3%~9%,with the increase of Mn content,the volume fraction of high temperature transformation products declines while the amount of low temperature transformation products increases,leading to the increased yield strength and tensile strength but decreased uniform elongation and total elongation.When Mn content increase to 12%,about 2% ε-martinsite and 1% austenite presents in the microstructure and they are easily transform to α-marteniste during early stage of straining,resulting in the increased uniform and total elongations and the illusion of decreased yield strength because of transformation plasticity.Since increased Mn concentration can decline the cohesion of grain boundaries,the impact energy of Fe-Mn alloys decreased sharply with the increase of Mn content.In order to obtain better comprehensive mechanical properties,the Mn content should be lower than 7% or higher than 12% to introduce more metastable austenite.