以低碳微合金钢为对象, 提出了一种利用相变进行亚微米化的新方法. 通过大变形 量温变形和循环淬火相结合的方法, 使奥氏体晶粒细化到1—2 μm. 在一般冷速的连续冷却条件下, 得到的 铁素体粒径接近或超过原奥氏体晶粒; 若 冷却过程中在Ar3点以下施加较大的变形, 则可以获得尺寸为0.1—0.3 μm的亚微 米级铁素体组织. 大变形量的温变形使得原始 组织中的碳化物分布均匀, 促进了加热过 程中碳化物的溶解及超细奥氏体晶粒的形成； 晶界滑动促进奥氏体的晶界形核可能是超细奥氏体 形变诱导相变的主要机制.
For low carbon micro-alloyed steel, a process of nanocrystallization of steels through transformation mechanism was investigated. The austenite grain size was refined to 1~2m through heavy warmly deformation intigrating with repeatly heating and quenching; under common continous cooling conditions, the ferrite grain size transformed from1~2m ultrafine austenite will be near to or larger than the original austenite grian size, i.e.,d/d>1;but if the heavy deformation was applied below Ar3 during cooling, the uniform and equiaxed ferrites with grain size of 0.1~0.3冚m, close to nanosize, can be obtained. The results indicate that heavy warm deformation can make the carbides in original microstructrures distribute uniformly, and this accelerate the dissolving of the carbides and the formation of ultrafine austenite. The main mechanism of deformation induced ferrite transformation of ultrafine austenite is that the nucleation of ferrite along austenite boundarie is enhenced by the boundary slipping of austenite grains.
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