珠光体转变中原子的位移及相变机制

Atomic Displacement and Mechanism of Pearlite Phase Transformation

研究过冷奥氏体转变为珠光体时原子的位移方式具有重要理论价值。以往认为,珠光体领域的长大依靠原子在奥氏体中的体扩散进行。新理论认为珠光体团的形核-长大是原子以界面扩散为主进行的相变。共析铁素体和共析渗碳体两相与母相奥氏体的相界面具有半共格,存在台阶,两相依靠共享台阶而长大。原子沿着阶面和台面的相界面扩散,每次位移距离为一个原子间距。珠光体团的迅速长大是界面扩散、两相的协同竞争长大机制。珠光体中的铁素体、渗碳体共析共生,共享台阶,是奥氏体"一分为二"的过程,不存在领先相。

It is significant theoretically to study the atomic displacement during pearlite phase transformation. It was once believed that the growth of pearlite colonies relied on the atomic diffusion in the austenite. The new theory suggests that the nucleation and growth of pearlite colonies are controlled by the interface diffusion. The phase interface between the eutectoid ferrite/the eutectoid cementite and austenite is semi-coherent,so there are steps. The growth of the eutectoid ferrite and the eutectoid cementite depends on the shared steps. The atoms can diffuse along the phase interfaces of the steps,which is an interfacediffusion process. The growth mechanism of a pearlite colony is synergistic competitive growth of the eutectoid ferrite and the eutectoid cementite,that is eutectoid and symbiotic process without the leading phase.