Shape Memory Alloys: A Material and a Technology

Abstract

Shape memory alloys offer attractive potentials such as: superelastic behaviour, reversible strains of several percent during heating or cooling over a limited temperature range, generation of high recovery stresses, and a work output with a high power/weight ratio. This paper describes the origin of those properties and gives an overview of the shape memory functions and shape memory applications. Fig. 1. Schematic representation of the volume transformed as a function of temperature.

Effects of Welding Parameters on the Mechanical Performance of Laser Welded Nitinol

“…B19 0 ) for most tensile specimens. 4,17) However, results showed evidence of an initial plateau in the welded specimens which became more pronounced with increasing peak welding power. This suggests an additional SIM transformation in the weld zone during straining before the usual pseudoelastic behaviour of the base metal.…”

“…17) In order to further detail the dual SIM transformation, a 2-cycle loading test was conducted. Figure 8 shows the first and second loading curves for the 0.9 kW, 10 pps weld condition, which was strained up to 0.06 mm/mm.…”

“…4,17) Remelting due to laser welding alters base metal microstructure, which for nitinol can result in the formation of dendrites or coarse grains and segregations at grain boundaries. [6][7][8] Furthermore, abnormal room temperature phase shifts in Nitinol due to laser welding have also been reported.…”

The Methods of Preparation of Ti-Ni-X Alloys and Their Forming

“…% (Raz & Sadrnezhaad, 2004), by decreasing the content of one element (Ti or Ni) to the prejudice of the third element, modified materials are obtained, while preserving some of original characteristics. Among the main characteristics, surpassing SME and SE, mechanical properties, corrosion resistance and related biocompatibility should be mentioned (Van Humbeeck, 2001) or (Duerig et al, 1999). Intermetallic equiatomic compound of nickel and titanium thus remains as the base of modified binary materials.…”

In-situ TEM cooling/heating experiments on deformed NiTi shape memory single crystals

“…for guide wires, orthodontic wires and stents [2,3]. In Micro-Electro Mechanical Systems (MEMS) the one-way effect is exploited in actuators and sensors [4][5][6][7]. In both fields, fatigue limits the service life of shape memory components.…”