|Number of page(s)||4|
|Section||Principles, Simulations, Materials: Background|
|Published online||01 September 2009|
Position of diffuse satellites appearing in Ti-44Ni-6Fe shape memory alloyMitsuharu Todai, Sho Majima, Takashi Fukuda and Tomoyuki Kakeshita
Department of Materials science and Engineering, Graduated School of Engineering, Osaka University, 2-1, Yamada-oka, Suita, Osaka 565-0871, Japan
Published online: 1 September 2009
We have investigated electron diffraction patterns of Ti-44Ni-6Fe alloy exhibiting a negative temperature dependence in electrical resistivity below Tmin = 210K. The electron diffraction patterns taken below Tmin show diffuse satellites at gB2+<ζ ζ 0>* when the zone axis is  B2 and  B2. For both beam directions, the value of ζ is slightly smaller than 1/3 and shows the same temperature dependence. On the other hand, the satellites are missing when the zone axis is  B2. This means that the incommensurate phase has a modulated structure with a propagation vector <ζ ζ 0>* (ζ ~ 1/3) and displacement direction is one of <110> which is vertical to the propagation vector. This modulation is obviously related to the softening of TA2 phonon branch with the propagation vector near 1/3<ζ ~ 0>*. In addition to the satellites at gB2+1/3<ζ ζ 0>*, satellites appear at gB2+<ζ ~ 0>* with ζ = 0.5 when the zone axis is  B2 and rod-like steaks appear in <ζ ~ 2ζ>* direction when the zone axis is  B2. However, these satellites and rod-like streaks do not show clear temperature dependence, suggesting that they are not directly related to the instability of the B2-type structure.
© Owned by the authors, published by EDP Sciences 2009