摘要
学术界普遍认为马氏体相变机制是切变机制,但与实际基本上不符.从理论分析和实验观察两方面综合论证了切变机制的缺陷,指出：（1）表面浮凸是相变体积膨胀所致,不具备切变特征,表明切变机制缺乏实验依据;（2）马氏体相变驱动力不足以克服相变阻力.切变消耗的切变能量太大,达208~320×10^3J/mol,远大于相变驱动力;（3）马氏体相变晶体学形核模型和切变长大模型均难以解释实验现象.半个世纪来不断改进仍然与实际基本不符,故切变机制是不成功的,并非成熟的理论,应于摒弃.探讨了新机制,指出马氏体相变是原子集体、协同的、无扩散的热激活跃迁位移,在此过程中马氏体中产生极高的位错密度,计算可达10^15×cm-2,与奥氏体保持半共格.新机制符合热力学条件,在晶体学、形态学上可解释实验现象.
Ahhough the shear mechanism is the generally accepted mechanism for martensitic transformation, it is inconsistent with the actual experiment. Herein the shear mechanism was demonstrated by means of integrated theoretical analysis and experimental observa- tion, and the results were obtained as follows： firstly, surface relief is caused by volume expansion of phase transition, which hasnt the characteristics of shear, indicating that the lack of experimental evidence for the shear mechanism ; secondly, driving force for martensi- tic transformation is not sufficient to overcome the phase change resistance; the energy for shear consuming is too much, about 208 - 320 ×10^3 J/tool - l, which is much larger than the driving force for transformation ; thirdly, it is difficult to explain experimental phenomena using the model of nucleation shear and growth model of martensitic transformation crystallography, which is still inconsistent with the basic reality after the continuous improvement for half a century, thus the shear mechanism is not mature yet. The new nechanism of martensitic transformation is discussed, showing that the transformation is the thermal activation transition displacement of atomic collection, collaboration, and non-proliferation; high dislocation density was produced in martensitic in the process, which remains semi-coherent with austenite. The new mechanism is consistent with the thermodynamic conditions; these experimental phenmena can be explained by crystallography and morphology.
出处
《内蒙古科技大学学报》
CAS
2009年第3期195-201,共7页
Journal of Inner Mongolia University of Science and Technology
关键词
马氏体
奥氏体
切变
浮凸
无扩散
热激活跃迁
位向关系
martensite
austenite
shear
surface relief
heat activation transition
orientation relationship
