·236 北京科技大学学报 2001年第3期 bic Boron Nitride Using Mg and pure or M-doped LiN, catalysts.Diamond Relat Mater,1993(3):75 Ca,N2,and Mg N,with N=A1,B,Si,Ti.J Mater Sci,1993, 3徐晓伟，刘志甫，赵会友，等，BC与NHCI生成BN反 28:1834 应的研究.材料研究学报，2000,15(2)：34 2 Nakano S,Ikawa H,Fukunaga O.Synthesis of Cubic Bor- 4徐晓伟，邹广田.氨化硼固相转变的船型模型.高压 on Nitride Using Li,BNa,Sr,B,N,and Ca,B:N,as Solvent- 物理学报，1992,3(6：217 Function of Ca,N2 in the Formation of BN ZHAO Hongmei,XU Xiaowei,LIU Zhifu,LI Yuping Material Science and Engineering School,UST Beijing,Beijing 100083,China ABSTRACT The function of Ca,N2 on the reaction between B.C and NH,C1 was investigated under normal pressure and high temperature.The results showed that there was small amount of hBN formed in the reaction at 950C,and little change took place after Ca,N2 was added.The amount of hBN achieved from the reaction at 1 200'C was more than that at 950C,and much more hBN was gained after adding CaN2.It was concluded that CaN:performed catalytic function in the formation of hBN.In addition,the results also indicated that the catalytic function of Ca,N:was less than that of LiN,and they could only act as catalyst at melting state. KEY WORDS Ca,N2;BN;LiN;catalyst 米米米米米米米米米米米米米米米米米米米米米米米米米米米米米米米米米米米米米米米米米米 Stability of Ultra-fine Microstructures during Tempering YANG Shanwu,SHANG Chengjia,HE Xinlai,WANG Xuemin,YUAN Yi Material Science and Engineering School,University of Science and Technology Beijing,Beijing 100083,China Abstract:The stability ofultra-fine microstructure during tempering at 650C was investigated on a Nb-containing steel.The steel had undergone 5 passes controlled rolling,then was relaxed(air cooled)to 730C and cooled in water.The evolution of micro- structure was that,in early stage of tempering,no obvious change was detected by means of optical microscopy while dislocation cells were formed inside bainitic laths.With further tempering,bainitic laths started to coalesce in some regions.Finally,polygonal ferrite was formed while hardness decreased dramatically.Some samples taken from the same primary plate were reheated at 930 C for 0.5h followed by quenching into water before tempering.Despite their lower original hardness,the reheated samples sof- tened faster during tempering.Ferrite was quickly formed in the reheated samples.These results indicate that the evolution of microstructures towards equilibrium during tempering of the steel is mainly determined by whether dislocations are pinned rather than the dislocation density. Key words:microalloyed steel;bainite;tempering [From Journal of University of Science and Technology Beijing,2001,8(2):119]一 北 京 科 技 大 学 学 报 年 第 期 ， ， ， 肠 ， ， ， ， ， ， 氏 犯 ， ‘ 丙 翻叮叻 ， 徐晓伟 ，刘志甫 ，赵会友 ，等 与 氏 生成 反 应的研究 材料研究学报 ， ， 徐晓伟 ， 邹广 田 氮化硼 固相转变的船型模型 高压 物理学报 ， ， 刀翔 口 阴， 不 ， 她 饭切 比 粉 ， 创的 丘 刃 曲 门 找 切吐 ， 胡 ℃ 吐比 ， ， 助 咖】 ， 翻 丘 如 如 ， 叨 ， 扭 ， 别刀口 ， 侧 构盯， 九 ，砰月 方触云 ， 别 万 明 理加 血 七 苗 毛戈 ， 吨 ， 运 五 场 七力 劝 位 ℃ 一 姗 ， ℃ 助 五 枉 成 ， 八 ， 峨 ， 币 、 ‘ 伪 旧 切火 而 ℃ ， 别 致堵 世勿 田叮 五 助 滋 比即 匡 枷 止 仰 触 ” 川。 舒 刀时葱昭 ，