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

作者：Jiao, Dong-Ling^*; Liu, Jiang-Wen; Luo, Cheng-Ping

来源：Transactions of Materials and Heat Treatment, 2007, 28(SUPPL.): 90-93.

• High nitrogen austenite
• Intermediate temperature transformation

In order to prepare a high-nitrogen austenite alloy with even nitrogen concentration for study, thin pure iron sheets of 0.1mm in thickness were through nitrided in ammonia gas at 640-650°C. The nitrogen content of high-nitrogen austenite was about 2.7 wt.% in this study. A microstructural study was carried out to clarify the nature of high-hardness produced in high-nitrogen austenite intermediate-temperature isothermal transformation at 225°C, 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.

• 出版日期2007-8
• 单位华南理工大学