EFFECTS OF Mn ON MULTI-PRECIPITATES EVOLUTION OF Cu-RICH AND NiAl PHASE IN STEELS

Precipitation hardened steels are widely used in various engineering fields due to their high strength, high fracture toughness, good ductility and ease of machinability. As two kinds of common precipitates, Cu-rich and NiAl phases play an important role on the mechanical properties of steels. The obvious effects of Mn on the precipitate evolution of Cu-rich phase and NiAl phase in steel have been observed respectively. However, the effect of Mn is complex, when Cu-rich phase and NiAl phase exist at the same time. This work aims to reveal the effects of Mn on the co-precipitation of Cu-rich phase and NiAl phase in steel. Fe-Cu-Ni-Al and Fe-Cu-Ni-AlMn steels were aged at 500 °C for different times after solution treatment at 900 °C for 2 h. Hardness testing indicates that by adding 2.17%Mn, Fe-Cu-Ni-Al-Mn steel shows a peak hardness of 420 HV which is 80 HV higher than Fe-Cu-Ni-Al steel (about 340 HV). And Fe-Cu-Ni-Al-Mn steel reaches the peak hardness at 1 h which is 1 h earlier as compared with Fe-Cu-Ni-Al steel at 2 h. Moreover, the peak hardness plateau of Fe-Cu-Ni-Al-Mn steel only lasts for 7 h which is far less than that of Fe-Cu-Ni-Al steel. All in all, the addition of Mn enhances the effect of precipitation hardening at early aging, and accelerates the whole process of precipitation hardening. Atom probe *国家自然科学基金钢铁联合基金培育项目U1460103和新金属材料国家重点实验室开放基金项目 2014-Z08资助 收到初稿日期: 2015-06-30,收到修改稿日期: 2016-03-01 作者简介:沈琴,女, 1992年生,硕士生 DOI: 10.11900/0412.1961.2015.00343 第513-518页 pp.513-518