钢中相变的自组织

Self-organization in the Phase Transformation of Steel

为深入探讨材料科学理论 ,研究钢中的相变机制 ,应用科技哲学的观点分析论述了钢的系统自组织特性。认为钢中的相变具有自组织功能和非线性相互作用。分析了钢在珠光体分解、马氏体转变、贝氏体转变等相变机理、组织形态等方面的自组织及其复杂性。认为相变机制一元化 ,组织形貌多元化。共析分解是个自组织过程 ,具有铁素体和渗碳体互为领先相的整合机制。马氏体相变首先产生“准马氏体”形式的结构涨落 ,通过位错或层错的运动 ,迅速放大这种涨落 ,使得原结构失稳 ,建构一种新结构 ,即马氏体晶体结构 ;以孪生切变完成马氏体相变 ,应当有孪生涨落 ,放大这种涨落 ,则以孪晶构成马氏体晶核。贝氏体转变在孕育期内 ,通过涨落必然形成贫碳区和富碳区 ;上贝氏体和下贝氏体有不同的转变机制 ,当然也有各自的转变动力学曲线。

In order to study the phase transformation mechanism of steel and to question the material science theory deeply,the method of science and technology philosophy was used to analyze and discuss the self organization property of steel in this paper.The author thought that there were self organization function and nonlinear interaction in the phase transformation of steel.The self organization and its complexity were analyzed in the phase transformation mechanism and the microstructure and morphology of the pearlite decomposition,martensite transformation and bainite transformation in steel.It showed that the phase transformation mechanism is mono unit and the morphology of microstructure is multiple unit.The eutectoid decomposition is a self organization process,which is characterized by the integrated mechanism that ferrite and cementite acted as prevenient phase alternatively.At first,the martensite transformation induced structural fluctuation,which presented quasi martensite form.The fluctuation was enlarged by means of the movement of dislocation or fault.As a result,the original structure became unstable and a new structure was built,i.e.martensite crystal structure.The twin fluctuation was sure to form when the martensite transformation was achieved by means of twin shear strain.When the fluctuation was enlarged,the martensite crystal nucleus appeared in the form of twin crystal.The bainite transformation during the incubative period was inevitable to form carbon leant zones and carbon enriched zones through the fluctuation.The upper bainite and lower bainite have different transformation mechanism and kinetics curve respectively.In fact,the morphologies of all kinds of microstructure are diversiform.