形变导致第二相分解是材料加工过程中普遍存在的现象，第二相的分解直接影响到材料的组织和性能。鉴于钢铁材料的重要性，过去数十年人们采用各种手段，对塑性变形导致珠光体钢中渗碳体（Fe3C）分解的现象进行了研究，但其中的基本问题仍然没有解决，争论还是存在。彻底搞清楚Fe3C的分解机制，对控制Fe3C的分解过程，进而优化钢铁产品的机械性能非常重要。同时对解释其他合金中形变导致第二相分解的现象也有借鉴意义。
本文首先通过高分辨电子显微术（HRTEM，High resolution transmission electron microscopy）表征了Fe3C中的位错，发现Fe3C中的位错具有不同于单质材料的特性，当其运动时可以改变滑移面及附近区域的微观结构。而后通过能量过滤像（EFTEM，Energy filtered transmission electron microscopy），电子能量损失谱技术（Electron energy loss spectroscopy, EELS）对Fe3C中位错运动对成分调制的现象做了进一步的研究，实验发现位错对成分调制的能力可能与滑移系有关。最后利用几何相位分析对高分辨图像进行了分析，并编写了相关程序，为计算机模拟位错核心结构打下基础。
其次对形变导致Fe3C分解的经典机制进行了研究。通过实验发现，对于中小变形量，片状Fe3C将在其表面产生大量台阶，极薄的Fe3C片甚至能产生均匀的弯曲，这将显著增大界面能，使得片状Fe3C的分解方式以热力学机制为主。而颗粒状Fe3C很难发生剪切形变，使得其表面有大量位错缠结，碳原子易与表面位错结合，其分解方式以位错机制为主。此外，根据实验结果推测：对于严重塑性变形，Fe3C的分解是一个复杂的过程，不同的阶段会由不同的机制来发挥主导作用。
其他摘要
Second phase decomposition is a very common phenomenon in cold deformation process in alloys. Because of its strong influence on the microstructure and mechanical property, it is necessary to make it clear in order to improve the manufacturability. In view of the wide applications of steel, in the past several decades, intense studies have been carried out on the deformation induced Fe3C dissolution in pearlite steel; two mechanisms are commonly accepted, while the basic mechanism on the dissolution is still under debate.
Firstly, studies on the composition modulation phenomena by moving dislocation in Fe3C phase was carried out by EFTEM and EELS. The experiment results indicate that the modulation ability of the dislocation in Fe3C might vary with the slip systems. Then geometric phase methods were used to analyze the strain field around the dislocation core for future computational study of this phenomenon.
Further more, classic mechanisms of deformation induced Fe3C dissolution were studied in this paper. It is found that the decomposition mechanism for lamellar pearlite steel is different from granular pearlite steels. The Fe3C phase in lamellar pearlite steels tends to decomposed through a thermodynamic mechanism, while in granular pearlite steels through a dislocation mechanism. At the same time, the experiment results reveal that Fe3C decomposition process is a dynamic process, which is the dissolution mechanism change with the microstructure evolution of the sample during plastic deformation. The Fe3C dissolution mechanism can not be determined only by the position of carbon atoms.
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