  Shape memory Ti-Ni alloys attracted much attention in the recent years, since
they are shape memory, intelligent as well as functional materials. In the
present investigation Ti51Ni49 and Ti51Ni45Fe4 alloys were synthesized through
radio frequency (RF) induction melting. The alloy was characterized through
x-ray diffraction (XRD), scanning electron microscopy (SEM), Mossbauer
spectroscopy (MS) and positron annihilation techniques (PAT).The Fe
substitution stabilized the TiNi type cubic (a=2.998 A) phase. The surface
microstructure and presence of the oxide layer in Ti51Ni45Fe4 alloy have been
investigated by SEM. The Positron annihilation measurements indicated a similar
bulk electron density in both the as-cast and annealed (1000 0 C for 30 hrs)
alloys, typically like that of bulk Ti. Mossbauer spectroscopy studies of
as-cast and annealed iron substituted samples showed regions in the samples
where nuclear Zeeman splitting of Fe levels occurred and an oxide phase was
found to be present in as cast Ti51Ni45Fe4 alloy, while annealed sample
indicated the presence of bcc iron phase .
