Premartensitic state of Ti-Pd-Fe shape memory alloys studied by electrical resistivity, magnetic susceptibility and specific heat measurements

Abstract

Transformation behavior in Ti-(50-x)Pd-xFe shape memory alloys has been investigated by electrical resistivity, magnetic susceptibility and specific heat measurements. The alloys with x = 14, 16 and 18 exhibit an obvious first order martensitic transformation, but the alloys with x= 19, 20 and 22 exhibit no first order transformation down to 4.2 K. However, the latter alloys show a negative temperature coefficient in electrical resistivity below a temperature Tmin, which decreases with increasing x. The increase in resistivity with decreasing temperature is associated with a decrease in magnetic susceptibility. Also, specific heat measurements at cryogenic temperatures have revealed that the electronic specific heat coefficient of the latter alloy s (x = 19, 20 and 22) is significantly larger than that of the former alloy s (x = 14, 16 and 18). These results suggest that the so-called precursor phenomena observed in Ti-Pd based shape memory alloys are caused by the instability of electronic structure of the B2-phase, as in the Ti-Ni based alloys previously studied by our group. ©2010 The Japan Institute of Metals.