The morphology and crystallography of martensite plates with a long period stacking structure in Ti-Pd shape memory alloy were investigated by transmission electron microscopy. In addition to B19 (2H) martensite, an 18R(21)6 structure was observed in equiatomic Ti-Pd alloy quenched above 1373 K. Three fundamental plate variant combinations were identified in the plate group in the region consisting exclusively of 18R martensite. These were designated A : B, A : C and A : Dtypes, and their morphologies and crystallographic characteristics are a wedge with type II, a spear with type I and a fork with compound twin relations, respectively. Duplex martensitic phases coexisting in the same area, namely, "two-in-one" structures, were also observed.
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