Modification and verification of the 'twinning shear' method according to phenomenological crystallographic theory of martensitic transformation

摘要

The phenomenological crystallographical theory of martensitic transformation has been successfully applied to many alloys [1], which has two mathematical methods ccomplished independently by different researchers i.e. the famous WLR and BM methods [2,3]. These two methods can produce same results, however, we think that original WL,R method may reflect more clearly the physical meaning of the transformation process. Firstly, the reason for appearance of the twin substructure was explained; secondly, the formation of the “invariant plane,” which is the principal basis of phenomenological theory, was considered as due to different Bain strains for martensitic matrix and twinned variant thus leading to offset of the shape strain totally. The original WLR method, however, has certain limitations, it can only explain formations of the (3,10,15), thin-plate martensites transformed from fee to bee or bet system in Fe-based alloys and of the martensites transformed from bee to orthorhombic system in In-Tl, Au-Cd alloys, but can’t explain the monoclinic martensitic transformations in Ti-Ni alloys and ZrO, cerimics, which both include the twin structure in martensite, the new problem about modifying the original WLR theory is thus put forward before us.