Study of relaxation and crystallization kinetics of NiTi made amorphous by repeated cold rolling

Autor(en)

Martin Peterlechner, Joachim Bokeloh, Gerhard Wilde, Thomas Waitz

Abstrakt

An amorphous structure of NiTi was obtained by repeated cold rolling. Relaxation and crystallization were studied applying a combination of sensitive calorimetric methods, X-ray diffraction and transmission electron microscopy. Upon deformation, a nanostructured mixture of crystalline and amorphous phase occurs. With increasing degree of RCR, the fraction of the crystalline phase decreases; at an equivalent strain of 16.8, an almost completely amorphous phase arises. Isothermal calorimetry yields a monotonously decreasing signal followed by a peak occurring by relaxation of the amorphous phase and nanocrystallization, respectively. The relaxation signal is well described by a Kohlrausch-Williams-Watts function. Crystallization kinetics agree with those expected from the Johnson-Mehl-Avrami model. The kinetic exponent agrees with three-dimensional growth and mixed nucleation or nucleation with a decreasing rate. The crystallization kinetics of NiTi made amorphous by severe plastic deformation differ from those of amorphous NiTi obtained by melt spinning or sputter deposition.

Organisation(en)

Physik Nanostrukturierter Materialien

Externe Organisation(en)

Universität Münster

Journal

Acta Materialia

Band

58

Seiten

6637-6648

Anzahl der Seiten

12

ISSN

1359-6454

DOI

https://doi.org/10.1016/j.actamat.2010.08.026

Publikationsdatum

2010

Peer-reviewed

Ja

ÖFOS 2012

103018 Materialphysik

Link zum Portal

https://ucrisportal.univie.ac.at/de/publications/da080e36-ff2e-4842-9126-591777e56903