氮对冷变形高氮奥氏体不锈钢微观结构的作用

Effects of nitrogen on microstructure of cold deformed high nitrogen austenitic stainless steels

利用透射电镜(TEM)对氮含量为0.66%和1.2%的高氮奥氏体不锈钢的冷变形微观结构进行了对比研究。结果表明,氮含量的增加提高了材料的层错能,强烈促进位错的平面滑移。冷变形过程中不断形成机械孪晶,机械孪晶随变形量的增加而减小,在60%变形量时只有几百纳米长。运用扩展位错和短程有序理论对氮的作用机理的分析表明,氮合金化引起的短程有序是促进位错平面滑移、提高材料加工硬化能力的主要因素,低层错能引起的位错扩展也有重要作用。

Microstructure of two cold deformed high nitrogen austenitic stainless steels（HNSs）,with 0.66% N and 1.20% N,respectively,was investigated by TEM.The results show that the stacking fault energy（SFE） of the steel increases with increase of nitrogen,which obviously promotes the planar slipping of dislocations in the steel.Mechanical twins are formed with cold deformation of the steel,which are decreases to only hundreds nanometer in dimension as the deformation increases to 60%.The effect of nitrogen in the steel is analyzed in terms of the extended dislocation theory and the short range ordering（SRO）.SRO caused by nitrogen is considered to be the most important factor that promotes planar slipping and increases the work-hardening ability for HNSs.The low SFE,which could cause the extension of dislocations,should also play an important role on the increase of work-hardening ability for HNSs.