Shape memory effects was first observed in 1932, an expensive and toxic alloy mixture of Gold-Cadmium. In the 1960s, the interest and research in shape memory greatly expanded upon the discovery of a Nickel-Titanium, a relatively inexpensive and non-toxic alloy. These unique metals made from combinations of two or more elements, exhibit hardness and elasticity properties that change radically at distinct temperatures.
After alloying and basic processing, Muscle Wires® can be formed into a shape such as coil spring and then set to that shape by a high heat treatment. When cooled, they may be bent, stretched, or deformed within certain limits. Then with subsequent moderate heating (well below the high heat setting temperature), they can recover some or all the deformation, and then move when heated.
Muscle Wires® can be found in numerous products and can be used to advance innovative technologies in industries such as aerospace, automotive, consumer electronics, and even medical devices. Other fields where Muscle Wires® have been used are space exploration (Clementine, Mars Pathfinder and many more) to arterial stents which restore blood flow to clogged arteries. Other industries and products including floral arrangement (animated butterflies and dragonflies) to actuators for miniature robots, cell phone antennas, orthodontic braces and even eyeglasses use Muscle Wires® for their extreme flexibility. So what is the difference between these shape memory alloy terms: Muscle Wires®, Nitinol, and Flexinol®? Excellent question! All these terms refer to a class of metal alloys having physical properties that change greatly at distinct temperatures (shape memory alloys), but the details of their performance, ease of use and what you can do with them varies widely. Muscle Wire® is a more generic term Shape Memory Alloys and Nitinol being one of the most common alloys used. Shape memory can also include items like springs and other shape set forms. Nitinol is a type of Shape Memory Alloy or MuscleWire®. While Nitinol is broadly used to reference shape memory alloys, there are many different types of nitinol. As-Drawn Nitinol, also known as cold worked nitinol silver in appearance, is not heat treated and would require heat setting. Flexinol® is a specific type of NiTi alloy, commonly referred to as actuator wire. Flexinol® is made using different methods than other shape memory alloys. Since Flexinol has been heat treated, the color of the wire may vary from amber to blue. The result is a product with more repeatable actuator wire properties. In short if Flexinol® is used within the acceptable parameters, you will see a very stable product having nearly the same parameters in both austenite (hot) and martensite (cold) phases over many cycles.