材料期刊网

利用热模拟压缩变形实验研究了不同形变温度以及形变速率下中碳钢过冷奥氏体形变过程的组织演变规律，探讨了中碳钢珠光体球化以及组织超细化的机理。实验结果表明：中碳钢过冷奥氏体的组织演变过程主要经历三个阶段，动态铁素体相变、动态珠光体相变以及珠光体的球化。为了获得亚微米级别铁素体和颗粒状渗碳体弥散分布的复相组织需要形变温度与形变速率的配合。形变过程中珠光体球化速率比等温球化退火快四个数量级，其原因是在形变过程中产生了高密度位错以及大量空位等缺陷，为碳原子的扩散提供了高速率扩散通道，促进了碳原子的扩散。渗碳体粒子在铁素体基体上的弥散分布可以用溶解－再析出机制来解释。

The microstructure evolution of a medium carbon steel (0.48%C) during deformation of undercooled austenite at different deformation temperature and strain rate has been investigated by means of uniaxial hot compression simulation experiment. The predominant mechanism on the formation of ultrafine (冄+冡) microduplex structures has been studied in medium carbon steel The experimental results showed that the process of microstructure development can be divided into three stages: dynamic ferrite transformation, dynamic pearlite transformation and spheroidization of lamellae pearlite. And the effects of deformation temperature and strain rate on the process of dynamic transformation and spheroidization of pearlite were different. A large number of vacanies and high density dislocations introduced during large strain hot deformation provided short-circuiting paths for diffusion of carbon atoms, as a result the rate of cementite spheroidization was accelerated by four orders of magnitude through deformation of undercooled austenite as compared to a static annealing treatment. The redistribution of cementite particles in the ferrite matrix has been observerd, which can be interpreted in terms of dissolution-reprecipitation mechanism.