Biomedical Engineering Reference
In-Depth Information
The dificulties discussed above seem to be very simple to
overcome, but in the light of the fact that the Ni-rich precipitation
forms compounds such as Ti
3
Ni
4
, Ti
2
Ni
3
, and TiNi
3
during ageing
process, it turns out to be more complicated [31].
Precipitations evoke the occurrence of the multi-stage
transformation behavior that introduces the R-phase orthogonal
structure between austenite and martensite and changes
characteristic transformation temperatures as shown in Fig. 8.24.
Figure 8.24
Thermal transformation with possible occurring sequence
behaviors of Ti-50.9 at% Ni wire form, after temperature
heat treatment [14].
The characterization of the mechanical behavior of a few
common NiTi alloys prepared by Myazaki and Otsuka gives certain
speciic ageing conditions used widely as reference for material
processing in research [27−28, 31].
Machining process such as drilling, milling, and turning are
possible, but they cause dificulties such as excessive tool wear.
Abrasive processes, laser machining, electro discharge machining,
and photochemical etching are more appropriate for this demanding
material. Most important, a cost-eficiency calculation needs to be
considered in the designing stage.
