高氮奥氏体中温转变高硬度的显微组织及其表征  

Microstructure and characterization of high hardness produced in high-nitrogen austenite intermediate temperature transformation

作　　者：焦东玲[1] 刘江文[1] 罗承萍[1] 

机构地区：[1]华南理工大学机械工程学院,广东广州510641

出　　处：《材料热处理学报》2007年第B08期90-93,共4页Transactions of Materials and Heat Treatment

基　　金：国家自然科学基金(50371028)资助

摘　　要：通过对0.1mm厚的纯铁片在640～650℃气体渗氮的方法制备含氮量均匀的单一高氮奥氏体,其含氮量约为2.7wt.%。利用光学显微镜、X射线衍射和透射电子显微镜研究了高氮奥氏体中温转变后的显微组织,初步确定了高氮奥氏体中温转变产生高硬度的原因是由于晶内纳米级γ′-Fe_4N相的析出后,在晶内形成(α-Fe+γ/γ′-Fe_4N)微纳级的晶粒,由这些微纳米颗粒引起的显微晶界强化是高氮奥氏体中温转变组织具超过常规时效强化的高硬度。In order to prepare a high-nitrogen austenite alloy with even nitrogen concentration for study, thin pure iron sheets of 0. lmm in thickness were through nitrided in ammonia gas at 640~650℃. The nitrogen content of high-nitrogen austenite was about 2.7 wt.% in this study. A microstructural study was carded out to clarify the nature of high-hardness produced in high-nitrogen austenite intermediate-temperature isothermal transformation at 225℃, using optical microscopy, X-ray diffraction （XRD） and transmission electron microscopy （TEM）. The results show that high-hardness produced during ageing process of high nitrogen austenite was due to form floccus cells consisted of nano-sized α-Fe laths and γ/γ＇-Fe4N laths interwoven with each other. The precipitate of nano-γ＇-Fe4N were precipitated and interspersed within ＂floccules＂. The grain boundary strengthening caused by the nano-sized microstructure and the precipitation hardening incurred by the tiny γ＇-Fe4N particles were believed to be jointly responsible for the ultra-high hardness of high nitrogen austenite intermediate temperature transformation.

关 键 词：高氮奥氏体 中温转变 γ'-Fe4N 显微结构 高硬度 

分 类 号：TG113[金属学及工艺—物理冶金]