Open Access
Article Number 02033
Number of page(s) 4
Section Principles, Simulations, Materials: Background
Published online 01 September 2009
ESOMAT 2009, 02033 (2009)
DOI: 10.1051/esomat/200902033

Position of diffuse satellites appearing in Ti-44Ni-6Fe shape memory alloy

Mitsuharu 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 [111] B2 and [100] 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 [110] 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 [100] B2 and rod-like steaks appear in <ζ ~ 2ζ>* direction when the zone axis is [110] 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