Papers by Author: Jakub Palka

Paper TitlePage

Authors: Danuta Stróż, Jakub Palka, Zdzisław Lekston
Abstract: In this paper a specific method of severe plastic deformation (SPD) applied to the NiTi shape memory alloy and the obtained structure and the alloy properties are presented. Cold rolling combined with transverse movement of the rolls was the method. The maximal strain obtained was εc ≈ 10.20 for the relatively large specimens. Then the alloy was annealed in order to obtain samples of a given grain size. In the paper the structure of the alloy annealed at 350°C was studied with the use of TEM equipped with Nanomegas attachment ASTAR allowing determination of the orientation of grains in nanoareas.
90
Authors: Danuta Stróż, Jakub Palka, Zdzisław Lekston, Agniwszka Smołka
Abstract: Ni-rich alloy (50.8at.%Ni) was plastically deformed by compression combined with reversion oscillating torsion. The compression rate was 0.05 mm/s and the torsion frequency and angle were 1,5Hz and ±3°. After the deformation process the specimens were annealed at 350°C/1h (623K/1h) and 400°C/1h (673K/1h). Their structure and transformation characteristic were studied with the use of TEM, X-ray phase analysis and DSC measurements. TEM observation of specimens after annealing at 350°C/1h (623K/1h) indicate presence of highly deformed B2 phase. In the specimen annealed at 400°C/1h (673K/1h) additionally Ni4Ti3 precipitates and the R-phase in the B2 matrix was found. DSC measurements show that the transformation sequence changes for the deformed and then annealed samples from single step B2  B19’ transformation to the B2  R  B19’ on cooling. Also increase of R-phase transformation temperature TR with the decrease of annealing temperature was observed.
339
Authors: Danuta Stróż, Jakub Palka, Zdzisław Lekston, Grzegorz Dercz
Abstract: The results presented here concern two NiTi alloys (near-equiatomic NiTi and Ni-rich alloy) subjected to plastic deformation by compression combined with reversion oscillating torsion. The maximal strain obtained was εc = 6.20. Finally the alloys were annealed at the temperature range 300 – 500°C for 1 hour. The structure of the as-prepared alloys was studied with the use of temperature X-ray diffraction and TEM observations. Also the DSC and bend and free recovery ASTM tests were carried out. It was found that the structure consists of a mixture of highly deformed B2 parent phase and B19’ martensite. The TEM studies revealed some amorphous areas in the most strained region of the samples. Annealing at lower temperatures caused formation of nanocrystalline structure that grew to the microcrystalline and finally well-defined polygonized structure in annealed at 500°C specimens. Multi-stage transformation was observed in the annealed at lower temperatures samples.
501
Showing 1 to 3 of 3 Paper Titles