nitinol sheets are one of the most exciting product forms on the market today. They are a unique form of shape memory alloy with two dimensional structure that can be processed in ways not possible with wire-based materials. It is a popular choice for laser cutting, EDM and photo etching applications to make complex devices with small scaled shapes.
The properties of Nitinol sheet and foil are controlled by the annealing steps used to produce it. Cold working, which occurs after hot working, is a critical part of the processing process that produces very high strength material. However, Nitinol is susceptible to fracture when it is not annealed.
During cold working, nitinol undergoes multiple complete annealing cycles to reach the desired level of strength. The final annealing step is followed by a heat treatment (thermomechanical processing).
A combination of heat treatment and cold working is the most common approach to the production of nitinol tubing, wires, and sheets. This approach minimizes the formation of hard titanium oxides and carbides. It also controls the oxygen content in the Nitinol melt.
The cyclic tensile test is the most commonly used testing method for determining nitinol’s mechanical properties. This cyclic test involves loading the material to a defined load to a specific strain and unloading it to the same load. The resulting tensile strength, ultimate tensile strength, upper and lower loading plateaus, and residual elongation are all important parameters in the testing of nitinol.