低碳微量铌钢形变过程中动态相变的特点  

Characteristics of dynamic transformation during deformation of undercooled austenite in Nb-microalloyed steel

作　　者：陈国安[1] 杨王玥[1] 郭守真[1] 孙祖庆[2] 

机构地区：[1]北京科技大学材料科学与工程学院,北京100083 [2]新金属材料国家重点实验室,北京100083

出　　处：《材料热处理学报》2006年第6期89-94,共6页Transactions of Materials and Heat Treatment

基　　金：国家973课题(2004CB619102);中信铌钢资助项目

摘　　要：用热模拟变形实验研究了低碳微量铌钢形变中的动态相变以及形变后冷却中的相变行为,透射电镜观察了Nb(CN)的析出及对铁素体晶粒截径和体积转变量的影响。结果表明含Nb钢动态相变中铁素体形核位置依次为原奥氏体晶界、铁素体/奥氏体的相界前沿直至奥氏体晶内,随着细小的应变诱导Nb(CN)析出在基体上弥散分布,铁素体的转变量大幅增加并且其相变长大趋势得到有效抑制,使得铁素体的长大在时间和空间上均受到限制,是一个以形核为主的过程,相变完成后铁素体晶粒截径约为2μm;而形变后冷却相变工艺中铁素体的形核位置主要为奥氏体晶界以及形变带,而大量弥散分布的Nb(CN)析出对细化铁素体晶粒的作用并不明显,是一个形核长大的过程,最终得到的铁素体晶粒截径约为7μm。Characteristics of dynamic transformation during deformation of undercooled austenite and the effects of Nb(CN) precipitations on ferrite grain size and volume fractions were investigated in Nb-microalloyed steels by means of hot compression simulation test and TEM technique. The experimental results show that during dynamic transformation of unercooled austenite ferrite grains nucleate on the prior austenite grain boundaries first, then at the areas in front of the interface between newly formed ferrite and austenite, and within the austenite grains finally. Furthermore with strain-induced precipitation of Nb(CN), ferrite volume fraction increases significantly and ferrite grain growth is suppressed by fine and disperse-distribution of Nb(CN) particles in space effectively because of the impingement of ferrite grains and the pinning of Nb(CN) particles. Therefore dynamic transformation during deformation of undercooled austenite is still a nucleation dominated process and as a result ferrite grain size is about 2μm when ferrite transformation accomplishs. However during static transformation the nucleation sites of ferrite are mainly the prior austenite grain boundaries and deformation bands. At the same time the effect of Nb(CN) precipitations on the refinement of ferrite grain size is not obvious, so the whole process is a mode of “nucleation and growth', as a result ferrite grain size is about 7μm when ferrite transformation completes.

关 键 词：低碳微量铌钢 动态相变 形核位置 Nb(CN)析出 

分 类 号：TG111.2[金属学及工艺—物理冶金] TG142.31[金属学及工艺—金属学]