Microstructure of Surface and Subsurface Layers of a Ni-Ti Shape Memory Microwire

作者：Tian H; Schryvers D^*; Shabalovskaya S; Van Humbeeck J

来源：Microscopy and Microanalysis, 2009, 15(1): 62-70.

DOI：10.1017/S1431927609090059

• nickel-titanium microwire
• TEM
• shape memory
• surface modification
• composition gradient
• surface oxide
• rutile
• Ni release
• EELS

The microstructure of a 55 mu m diameter, cold-worked Ni-Ti microwire is investigated by different transmission electron microscopy techniques. The surface consists of a few hundred nanonleter thick oxide layer composed of TiO and TiO(2) with a small fraction of inhomogeneously distributed Ni. The interior of the wire has a core-shell structure with primarily B2 grains in the 1 mu m thick shell, and heavily twinned B19' martensite in the core. This core-shell structure can be explained by a concentration gradient of the alloying elements resulting in a structure separation due to the strong temperature dependence of the martensitic start temperature. Moreover, in between the B2 part of the metallic core-shell and the oxide layer, a Ni(3)Ti interfacial layer is detected.

• 出版日期2009-2