Abstract
The present work aims to clarify the atomic arrangements at the austenite/martensite interfaces for the nucleating martensite and the growing tip of martensite plates. An Fe-23Ni-3.8Mn alloy and an Fe-9Cr-1.1C alloy with the K-S orientational relationship with the {112} habit plane were observed with high resolution electron microscopy. At the very tip of the wedge-shaped growing martensite, dislocations queue up on about every six (111)f layers along the interface, with their extra-half plane in the austenite. A nucleus of the martensite was observed in the Fe-9Cr-1.1C alloy. The nucleus has the K-S orientational relationship with a habit plane of (111)f(||(011)b), a wing-like shape, and remarkably expands in the direction of [\\bar101]f(||[\\bar1\\bar11]b). The crystal structure of the nucleus shows a transient lattice region from fcc to bct toward the inside, and the transformation into the final martensite structure (bct) is still incomplete even at the center of the nucleus.
