马氏体组织形貌形成机理

Formation Mechanism of Martensite Morphology

研究马氏体组织形貌形成机理具有重要的理论意义和工程价值。马氏体的形貌复杂,有板条状、片状、蝶状、薄片状、针状、“透镜”片状、隐晶状等;以往以切变机制衍生的各类学说解释马氏体组织形貌的成因,均不正确。实验研究表明,奥氏体→马氏体相变时的体积应变能是影响马氏体组织形貌的主要原因。马氏体的形核-长大是按照能量消耗最小的途径进行的,沿着应变能最小的晶向、晶面长大,形成不同的马氏体组织形貌。隐晶马氏体也是条片状,其形成与奥氏体晶粒内的成分不均匀性有关。

It is significant in theory and engineering practice to study the formation mechanism of martensite morphologies. The morphologies of martensite are complicated with the shapes in lath, plate, butterfly, thin slice, needle, convex lens, cryptocrystal and so on. The past theories derived from the shear mechanism can not explain the formation mechanism of martensite morphologies correctly. The experimental studies show that the volumetric energy resulted from the transformation from austenite to martensite is the main cause affected the martensite morphologies. The nucleation and growth of martensite follow the principle of the lowest energy consumption. That is the martensite nucleus grows along the crystallographic orientation and the crystallographic plane with the smallest strain energy then forms the different morphologies. The cryptocrystalline martensite is also plate martensite, and the formation mechanism of it is attributed to the composition inhomogeneity in austenite grains.