A unique feature of lath martensite

A unique feature of lath martensite is the alignment of martensite crystals in parallel or almost parallel arrays. The crystallographic orientations of the effectively parallel crystals may be i d e n t i c a l o r m a y v a r y .[13]Where the effectively parallel crystals have somewhat different orientations, the crystals are arranged in units termed packets, and the units in which the martensite plates have the same crystallographic and habit plane orientations have been termed blocks.[14]Figure 2 shows two packets of martensite crystals formed on opposite s i d e s o f a n a u s t e n i t e g r a i n b o u n d a r y . W i t h i n e a c h o f those packets crystals of martensite have two roughly parallel intertwined habit plane orientations. The habit plane in lath martensite has been determined by two surface analysis to be {557}ɤ,[13]close to {111}ɤand, therefore, the two closely spaced habit planes in each packet shown in Figure 2 may be different variants of {557}ɤaround one of the four {111} planes in a parent austenite crystal.