Biomedical Engineering Reference
In-Depth Information
Figure 8.20
Sequence of transformation after training in SMA [13].
8.5
Receiving of Nickel-Titanium
Shape Memory Alloy
For the receiving of NiTi is crucial to maintain high-purity
requirements. Slight luctuation of composition causes a strong
deviation in temperatures of the transformation. For instance, 1%
shift in the amount of composition can cause a 100°C change, as
shown in Fig. 8.21.
It is very important to control a manufacturing process using
proper methods and protective atmospheres. Usual melting
methods employed to obtain pure titanium such as electron beam
melting (EBM), vacuum induction melting (VIM), and vacuum arc
remelting (VAR), are used to mix well the composition and achieve
ingot homogeneity and uniformity [31].
Figure 8.21
Schematic of the effect of the element content on the alloy
phase transformation temperature [33].
The impurities mainly result from elemental raw materials,
atmosphere, or crucible materials. Oxygen content in the alloy
