Energetic stability of boundary between variants in lath martensite

Highlights: ► We calculated interfacial energy of different K–S variants by using molecular dynamics simulation. ► A group of laths of the same K–S variant with small misorientation varied from 0° to 5.5°/[0 1 1]α′, will have smaller interfacial energy than combination of different K–S variants. ► Boundary between different K–S variants will have the smallest interfacial energy in case of twin-related variant pairs. -- Abstract: In this study we have evaluated the energetic stability of boundaries between Kurdjumov–Sachs (K–S) variants to explain the morphology of sub-block and block in lath martensite. Interfacial energy of different variant pairs was calculated by using molecular dynamics simulation. Three dimensional models of tilt and twist boundary with a method evaluating interfacial energy were developed. The results showed energetic stability of twist boundary with small misorientation from 0 to 5.5°/[0 1 1]α′ in consistence with previous transmission electron microscope observation. For other boundary with larger misorientation, the twin-related variants had the smallest interfacial energy although this variant pair was not frequently observed in electron backscatter diffraction analysis