Characterization and properties of a modified NiTi shape memory alloy by N+ ion implantation.

Marek S. Michalec 1Zbigniew Świątek 2Tomasz Czeppe 2Nela Levintant-Zayonts 3Stanisław Kucharski 3Oleksandr Y. Bonchyk 4Grigorij Savitskij 4

1. Jagiellonian University, Faculty of Chemistry, Ingardena 3, Kraków 30-060, Poland
2. Polish Academy of Sciences, Institute of Metallurgy and Materials Sciences (IMIM PAN), Reymonta 25, Kraków 30-059, Poland
3. Polish Academy of Sciences, Institute of Fundamental Technological Research (IPPT PAN), Świętokrzyska 21, Warszawa 00-049, Poland
4. Institute of Applied Problems of Mechanics and Mathematics (IAPMM), 3B Naukova Str., Lviv 79060, Ukraine

Abstract

NiTi alloys with a near equiatomic composition exhibit excellent shape memory effect, superelasticity, corrosion resistance and biocompatibility, tolerance to severe environmental conditions, and thus is one of the most important engineering materials. Their particular and superior properties are caused by a reversible thermoelastic martensitic transformation. NiTi shape memory alloys has been modified by N+ ion implantation. In general, implantation process may be one solution to enhance the mechanical properties of surface, corrosion, wear and fatigue resistance of such instruments. The ion implantation method has precision capabilities for modification of thin surface layers on metals and alloys including their chemical composition, crystal structure, physical and mechanical properties.

The presented work is aimed at the investigation of structural changes in the modified near-surface layer of NiTi alloy, caused by ion implantation as well as at their influence on the mechanical and shape memory properties of this material. The investigations were carried out on an equiatomic commercial NiTi shape memory alloy. In the process of ion implantation of nitrogen at dose 1018cm-1 and 55keV energy, the well-defined double-layer structure with different microstructure as well different chemical and phase composition was formed.

Differential scanning calorimetry was used to characterize the transformation sequence and transformation temperatures for the initial and surface-modified materials. The modifications of the phase composition before and after irradiation are studied at the room and martensitic transformation temperatures by X-ray diffraction methods.

Experimental results of an structural-phase condition and functional mechanical properties of NiTi alloys are compared and discussed in this paper.l

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Presentation: Poster at E-MRS Fall Meeting 2007, Symposium E, by Marek S. Michalec
See On-line Journal of E-MRS Fall Meeting 2007

Submitted: 2007-05-14 12:04
Revised:   2009-06-07 00:44
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