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Structure and shape memory effect in annealed Ni-Ti-Co strip produced by twin roll casting technique

Tomasz Goryczka 

University of Silesia, Institute of Materials Science, 12, Bankowa Str., Katowice 40-007, Poland


Ternary Ni-Ti-Co alloy belongs to a large  family, which reveals shape memory effect (SME). Addition of cobalt causes changes in thermal behavior as well as sequence of the martensitic transformation. Applying twin rolls casting, rapid solidification, technique for shape memory alloy (SMA) production significantly influences microstructure and grains formation. Additional thermal treatment opens wide possibility in steering of transformation behavior.

In reported results the ternary  Ni47Ti50Co3 alloy was produced using twin rolls casting technique. Optimized processing parameters allowed to obtain polycrystalline strips 25 cm long, 45mm wide and 300um thick. The samples were cut from the central part of the strip and subjected to annealing at 3000C, 4000C, 5000C for 1 hour. Annealing was carried out in real condition without protection atmosphere. The as-cast strip reveals two stages in the range of the martensitic transformation. It is a consequence of increase in dislocation density  introduced during cold-rolling, which is realized during twin rolls casting. Annealing causes reduction of dislocation density and one stage of the martensitic transformation was observed. Also, shape recovery of the annealed strip is discussed. The effect was measured as  elongation versus change of temperature under constant load.


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Presentation: Poster at E-MRS Fall Meeting 2008, Symposium C, by Tomasz Goryczka
See On-line Journal of E-MRS Fall Meeting 2008

Submitted: 2008-05-08 11:16
Revised:   2009-06-07 00:48