Showing papers by "Miroslav Karlík published in 2017"
TL;DR: In this article, the effect of annealing a Ni-48at.%Ti alloy prepared by self-propagation high-temperature synthesis (SHS) by means of transmission electron microscopy (TEM) was studied.
Abstract: The effect of annealing a Ni–48at.%Ti alloy prepared by self-propagation high-temperature synthesis (SHS) by means of transmission electron microscopy (TEM) was studied. The alloy in the as-sintered condition shows the presence of B2 NiTi matrix, relatively large particles (2–100 μm) of cubic NiTi2 phase and very fine densely distributed particles of rhombohedral Ni4Ti3 phase. The phase fractions were determined by the Rietveld refinement of neutron diffraction. Twelve-hour annealing at 1000 °C leads to coarsening of Ni4Ti3 particles. Slow furnace cooling from the annealing temperature results in a transformation of the rhombohedral Ni4Ti3 phase to a metastable Ni3Ti2 phase with cubic symmetry. Its particles, coherent with the B2 matrix, have the form of thin oval platelets with lenticular cross-section. The orientation relation is either cube-to-cube or [115]B2 || [111]P and (552)B2 || (121)P. An additional isothermal annealing of the water cooled samples at 720 °C for 3 and 10 h was carried out....
13 citations
TL;DR: In this article, the structure of Ni8Ti5 was solved and refined from precession electron diffraction tomography data using dynamical refinement approach using trigonal symmetry R-3m (a = 12.24m, c = 15.33m).
8 citations
TL;DR: In this article, the effect of reaction atmosphere and heating rate during reactive sintering of nickel and titanium powder blend (Ni: 52 at.99% purity, Ti: 48 at.5% purity) were studied.
8 citations
TL;DR: In this paper, various alloying elements (Al, Si, Mg, Fe, Nb, V) were added to Ni-Ti alloy in order to lower the amount of Ti2Ni phase or at least to minimize its undesirable effect on the alloy properties.
Abstract: NiTi alloy is usually prepared by casting and forming. As an innovative process, reactive sintering powder metallurgy is tested worldwide, aiming to prepare pure NiTi alloy easily from nickel and titanium powders. This process enables to prepare both porous and low-porosity alloy, depnding on the process conditions. However, the formation of NiTi phase in this process is always accompanied by the Ti2Ni phase, which is hard, brittle, less corrosion resistant and does not have the shape memory. In this work, various alloying elements (Al, Si, Mg, Fe, Nb, V) were added to Ni-Ti alloy in order to lower the amount of Ti2Ni phase or at least to minimize its undesirable effect on the alloy properties. The reactive sintering behaviour, phase composition and mechanical properties of Ni-Ti-X alloys were described.
6 citations