Three-dimensional characterisation of precipitates in Ni-Ti shape memory alloys by slice-and-view in a FIB-SEM dual-beam microscope.

Ni-Ti based alloys are at present the mostly used materials in shape memory and superelastic components for applications in a wide variety of fields ranging from stents and orthopedic wires in the medical sector over mechanical actuators to various clutching devices. The martensitic transformation from a cubic B2 austenite structure to a monoclinic B19' martensite structure is the basis for this special behavior. Depending on the application different compositions are used, usually around the equiatomic 50-50, although recently a lot of research has been conducted into ternary systems (with additions of Cu, Hf, Zr, Au, Pt, Pd). The starting material receives a specific thermal treatment resulting in the growth of nano- to micron sized precipitates with type, size and distribution depending on temperature, period of the treatment and possible external stress conditions. These precipitates have a concrete influence on the phase transformation behavior and functional conditions of these materials. A proper understanding of their three-dimensional distribution is thus of crucial importance for the further development of this technology, e.g., in the direction of the important higher temperature domain for applications in the context of engines.

Keywords:ELECTRON MICROSCOPY, ALLOYS, PHYSICS

Disciplines:Condensed matter physics and nanophysics, Ceramic and glass materials, Materials science and engineering, Semiconductor materials, Other materials engineering

Project type:Collaboration project