共析钢的过冷奥氏体动态相变和组织超细化  

DYNAMIC TRANSFORMATION OF UNDERCOOLING AUSTENITE AND MICROSTRUCTURE REFINEMENT IN A EUTECTOID STEEL

作　　者：黄青松[1] 李龙飞[1] 杨王玥[2] 孙祖庆[1] 

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

出　　处：《金属学报》2007年第7期724-730,共7页Acta Metallurgica Sinica

基　　金：国家自然科学基金项目50471092;教育部博士点基金20050008017资助~~

摘　　要：通过在Gleeble-1500热模拟试验机上进行单轴热压缩实验,研究了共析钢中过冷奥氏体在A_1-A_(r1)之间变形时的组织演变,探讨了共析钢中复相组织球化超细化的机理．结果表明:随着应变量的增加,片层珠光体在原始奥氏体晶界形成的铁素体生长前沿形核长大,并向原始奥氏体晶内推进,直至相变完成．片层珠光体生成后继续变形,发生渗碳体的溶断和球化,及铁素体的动态回复再结晶等轴化等过程．渗碳体的球化有两种机制,其一是由于Gibbs-Thomson效应,珠光体中片层状渗碳体发生溶断和球化,生成的大颗粒渗碳体主要分布在铁素体晶界;其二是纳米级渗碳体粒子伴随铁素体动态再结晶在晶内重新析出．实验证实,在合适的变形工艺条件下可以得到亚微米级铁素体与亚微米、纳米级颗粒状渗碳体的双相组织．Hot uniaxial compression tests were performed on a eutectoid steel using a Gleeble- 1500 hot simulation test machine. After austenized at 850 ℃, the specimens were cooled quickly to temperature between A1 and Ar1, and then deformed at various strain rates. With the increase of strain, pearlitic lamellae nucleated and grew in front of the proeutectoid ferrite formed along the grain boundaries of prior austenite. And then, dynamic pearlite transformation became the predominant process of dynamic transformation until the decomposition of austenite completed during deformation. After pearlite formed, there are two spheroidization process for lamellae under further deformation： firstly, The presence of bends and kinks of the lamellae led to the dissolution of lamellae through the Gibbs-Thompson effect, resulting in the coarse particles of cementite formed at the grain boundaries; Secondly, with the dynamic recovery and recystalization of ferrite, the fine carbides reprecipitated in the ferrite. At the same time, the Ostwald ripening made the number of fine particles decreased gradually. The duplex microstructure consisting of sub-micrometer ferrite grains and cementite particles can be obtained under proper deformation conditions.

关 键 词：共析钢 过冷奥氏体 动态相变 铁素体动态再结晶 组织细化 渗碳体球化 

分 类 号：TG142.1[一般工业技术—材料科学与工程]