On the martensitic transition manner within the transition martensitic zone of the dissimilar steel interface

The transition structure of BCC/FCC dissimilar steel interface shows outstanding property compared with homogeneous structure. The formation of the transition structure is closely related to the martensitic transition manner. The accommodation mechanism for martensitic transformation was analyzed through multi characterization methods. The results indicate that, within the transition martensite zone (TMZ), micro to nano scale accommodation mechanisms is invoked in sequence to respond the variation of transition condition. By micro scale accommodation (>μm), the martensitic structure minimizes their sizes (from coarse lath to thin plate structure) to decrease the inhomogeneity within one lath due to the change of composition. By sub-micro scale accommodation (nm < … < μm), the martensite develops from the preferential planes, showing variant selection to accommodate with thermal stress. The EBSD maps indicate that TMZ has a G-T relationship, and selects the preferential transition planes first, then the highest U variants, and finally its variant pair that shares the same Bain axis with prior forming martensite. TEM&HTEM analysis shows that TMZ derives a nesting growing mode (NGM) to achieve nano scale accommodation. The main martensitic plates develop along {111}fcc first. The adjacent martensitic plates derive from {112}bcc of the main plates taking advantage of similar atomic arrangement.