块状转变与钢中贝氏体相变的亲缘关系——再论贝氏体相变的切变-扩散整合机制

The blood relationship between massive transformation and bainite transformation in steel——Further discussion of the shear-diffusion integrated mechanism of bainite transformation

应用JEM-2010高分辨电镜和Quanta-400型环境扫描电镜,运用试验与综合分析的方法,研究了纯铁的块状转变和钢中的贝氏体相变,通过对相变的形核、长大,贝氏体亚单元和组织的形成的综合研究和分析,认为贝氏体相变与块状转变存在亲缘关系.依靠随机涨落,形成贫碳区,贝氏体铁素体在贫碳的奥氏体中形核.Fe原子和替换原子通过热激活跃迁、界面扩散或切变等方式,重复产生亚单元.在亚单元边界处,富碳奥氏体析出碳化物或成为残留奥氏体.贝氏体相变机制具有过渡性,即切变扩散整合机制.

The massive transformation of pure iron and bainite transformation in steel were discussed via experimentation and synthesis analysis by means of JEM-2010 HREM and Quanta-400 SEM. The nucleation and growth of phase transformation, the form of bainitic subunits and mierostruetures were studied. The results show that there is a relationship between massive transformation and bainite transformation. Carbon-poor area forms by way of random fluctuation and carbon atom diffusion. Bainitie ferrites nucleate in carbon-poor austenite. Fe atoms and replace atoms bring forth subunits continuously at interphase and in austenite by heat activation transition, interphasc diffusion and or shear mode. Either ε-carbide can be precipitated or the retained austenite remains from carbon-rich austenite at subunit boundary .It is put forward that the bainite transformation has transition characteristic, namely, diffusion-shear integrated mechanism, which is the bainitie transformation mechanism.