细晶强化和位错强化对中锰马氏体钢的强化作用

Effect of Grain Refinement Strengthening and Dislocation Strengthening on Strength of Medium Manganese Martensitic Steels

研究了碳和锰含量对淬火中锰马氏体钢的位错密度、残余奥氏体含量、晶粒尺寸等组织结构以及室温力学性能的影响。借助于SEM、EBSD、TEM和XRD表征了材料的微观组织,探讨了马氏体钢的强化机制。结果表明:随着碳含量增加,淬火中锰钢的位错密度和残余奥氏体体积分数逐渐增加,板条束和板条块尺寸逐渐细化,大角晶界百分数逐渐增加,强度逐渐升高;增加锰含量能够提高马氏体钢的位错密度和抗拉强度。分析认为,位错强化和细晶强化是淬火中锰马氏体钢的主要强化机制。马氏体板条尺寸是马氏体抗拉强度的结构控制单元,而原奥氏体晶粒尺寸则是马氏体屈服强度的结构控制单元。

Effect of carbon and manganese content on the mechanical properties and microstructure characteristics of the medium manganese steels quenched in oil,such as dislocation density,volume fraction of retained austenite and grain size were investigated.Microstructures of the medium manganese steels were observed by SEM/EBSD,TEM and XRD techniques and tensile test was conducted at room temperature to examine their mechanical properties.Strengthening mechanisms operating in martensitic steel and the effects of carbon content on the strengthening contributions of the grain refinement and dislocation were discussed.It is found that increasing the carbon content increases the dislocation density,volume of retained austenite and the percent of high angel grain boundaries,but decreases the size of packet and block.This in turn increases the yield strength and tensile strength.Increasing manganese content increases the dislocation density and tensile strength.Dislocation strengthening and grain refinement strengthening are the main strengthening mechanisms operating in as-quenched martensitic steels.According to the strengthening calculation,it is proposed that the microstructure unit controlling the strength of martensite steels is the pre-austenite grain size for the yield strength but the lath size for the tensile strength.