|
Microdefects and free electron densities in near-equiatomic NiTi alloys
of five different chemical compositions have been studied by positron
lifetime measurements. The results indicate that some 3d electrons are
localized to form covalent bonds when Ni and Ti atoms aggregate to form
NiTi alloys, leading to the decrease of the free electrons participating in
metallic bonds. The densities of free electrons in the bulk and defects of
near-equiatomic NiTi alloys change with the increase of Ni content and
reach the maximum value with 51.0% Ni (atom fraction). It is also found
that the Ni"5"1Ti"4"9 alloys have the fewest defects, which contributes to
the Martensite transformation. Consequently, the Ni"5"1Ti"4"9 alloys have
the best shape memory effect.
|
