Abstract

WAITZ, Thomas. Bulk nanostructured shape memory alloys. C.Tecn. Mat. [online]. 2008, vol.20, n.1-2, pp.25-29. ISSN 0870-8312.

This paper starts with a brief introduction to bulk nanostructured materials. Bulk nanocrystalline materials processed by methods of severe plastic deformation show mechanical properties and phase structures that can differ significantly from those of their coarse grained counterparts. In the case of NiTi shape memory alloys, a nanocrystalline structure is obtained via the devitrification of an intermediate amorphous phase induced by high pressure torsion. Grain sizes in the range of 5 to 350 nm are achieved that are free of strains and of crystal defects. The small grain size significantly impacts the martensitic phase transformation that causes unique thermomechanical properties such as the shape memory effect and superelasticity. Experimental results on the enhanced mechanical properties of nanocrystalline and ultrafine grained NiTi shape memory alloys are shortly reviewed.

Keywords : Nanostructures; Severe plastic deformation; Shape memory alloys; Martensite; Size effect.

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