Dresden 2011 – wissenschaftliches Programm
Bereiche | Tage | Auswahl | Suche | Aktualisierungen | Downloads | Hilfe
MM: Fachverband Metall- und Materialphysik
MM 45: Topical Session Heterogeneous Nucleation II
MM 45.4: Vortrag
Freitag, 18. März 2011, 11:15–11:30, IFW B
Effect of production route on microstructural development during heat treatment of nanocrystalline NiTi and NiZr alloys — •Reeti Singh1, Sergiy Divinski1, Harald Rösner1, Ruslan.Z Valiev2, and Gerhard Wilde1 — 1Institut für Materialphysik, Westfälische Wihelms-Universität Münster, Wilhelm-Klemm-Str. 10, 48149, Münster, Germany — 2Institute of Physics of Advanced Materials, Ufa State Aviation University, 12 K. Marx Street, 450000 Ufa, Russian Federation
A comparative study of an amorphous NiTi alloy, produced by severe plastic deformation via high-pressure torsion (HPT) and a NiZr alloy, produced by HPT, repeated cold rolling (RCR) and melt-spinning (MS), is presented. The microstructure evolution is investigated in dependence on the production route by differential scanning calorimetry (DSC), X-ray diffraction analysis and transmission electron microscopy. The DSC signals observed during continuous heating experiments indicate a large separation between the crystallization and growth stages in the amorphous NiTi and NiZr alloys. A detailed analysis of the evolution of the enthalpy release revealed reproducibly non-monotonous trends with the annealing temperature that cannot be explained solely with nucleation and growth of crystalline volume fractions. However, these results as well as detailed kinetics analyses indicate that a reverse amorphization process occurred during annealing around 523 K in the NiTi alloy. The vitrification and crystallization characteristics of NiZr amorphized by HPT, RCR and MS are analyzed for comparison.