Morphology and Crystallography of Martensite Plate with Long Period Stacking Structure in Ti-Pd Shape Memory Alloy

Abstract

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 18Rð2 1 1Þ 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 : D types, 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.

Novel long-period stacking-ordered structure of martensite in zirconium–cobalt–palladium alloys

“…In Otsuka's notation, the B33 structure is represented as a 4O (orthorhombic) structure in terms of the number of stacking layers and the Bravais lattice [4]; we, therefore, refer the B33 structure as a 4O structure henceforth. Many martensitic phases have been reported to possess a long-period stacking-ordered (LPSO) structure, for example, 18R in Cu-Al alloys [5], 9R in Cu-Zn alloys [6], 7R (14 M) in Ni-Al [7] alloys, 10 M and 14 M in Ni-Mn-Ga alloys [8,9] and 18R in Ti-Pd [10] alloys. Variations of the LPSO structure in these alloys have also been reported.…”