中文摘要：

利用热模拟压缩变形实验以及SEM、XRD和热磁法，研究了中碳钢过冷奥氏体变形时组织演变过程中碳原子的分布与扩散．结果表明，动态相变过程中碳的有效扩散系数与等温过程相比明显增大，相变完成时间显著缩短．在随后的片层状珠光体的球化过程中，相界以及形变过程中产生的高密度位错和空位等缺陷促进了间隙碳原子的扩散，使得球化动力学过程与等温退火相比显著缩短．渗碳体的溶解和铁素体中碳的过饱和现象得到证实，其中过饱和碳原子高度聚集在铁素体晶界和位错核心处，而不是均匀地分布在铁素体点阵的间隙位置．

英文摘要：

The distribution and diffusion of carbon atoms during deformation of undercooled austenite in the medium carbon steel were investigated by means of uniaxial hot compression simulation experiment, SEM, XRD and thermomagnetic methods. The experimental results showed that the effective diffusion coefficient of the carbon atoms during dynamic transformation of undercooled austenite increased significantly compared with that during the isothermal transformation at the same temperature, as a result the completion of ferrite and pearlite transformation was shortened. During the subsequent spheroidization process of lamellae pearlite, high density dislocations and vacanies in- troduced during hot deformation promoted the diffusion of the carbon atoms, therefore the cementite spheroidization kinetics was accelerated dramatically as compared to isothermal annealing treatment. The dissolution, re-precipitation of cementite, and supersaturation of carbon inside the ferrite grains were confirmed. The supersaturated carbon atoms were not located at interstitial sites within the iron lattices homogeneously, but highly segregated at ferrite grain boundaries and dislocation cores.