Mn含量对Fe-Mn合金组织及力学性能的影响

利用扫描电镜、透射电镜、背散射电镜及拉伸和冲击试验研究了锰对含锰量为3%~12%的Fe-Mn合金组织和力学性能的影响。结果表明,当锰含量介于3%~9%时,随着锰含量的上升,高温相变产物(多边形铁素体和准多边形铁素体)受到抑制,合金的屈服强度和抗拉强度逐渐增加而均匀延伸率和总延伸率逐渐下降;当锰含量增加至12%时,合金中残留的少量亚稳ε马氏体和奥氏体在形变初期发生相变,产生的相变塑性使合金呈现出屈服强度下降的假象,但合金的抗拉强度、均匀延伸率和总延伸率均上升。由于晶界锰原子浓度的增加会减弱界面的结合力,故合金的冲击韧性随锰含量的增加而显著下降。为使Fe-Mn合金获得较好的综合力学性能,应控制锰含量小于7%或在基体中引入适量的亚稳相。

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.