High Resolution Electron Microscopy Studies on the Interface Structure of Martensite Variants in a Ti-Ni-Hf Shape Memory Alloy

摘要

The substructure and the intervariant boundary structure of martensite in the Ti_36Ni_49Hf_15 alloy have been investigaed by high resolution electron microscopy (HREM). (001) compound twin and (001) stacking faults were confirmed to be the main substructure inside a martensite variant with some (001) stacking faults infrequently observed. The feature of the (001) twinning boundary was staight with some blurred region and (001) faults existing enar the interface. A new general morphology was found to be wedge-like martensite variants having a (111) Type I twinning relation, which showed a wavy interfacial feature. The 9001) Type I and <001> Type II with were revealed to exist to exist at the junction planes between spear-like and mosatic-like martensite variants, with the interfacial characteristic similar to that in the TiNi alloy.