9 things to consider when treating metals: 7

How does alloy composition affect metal heat treatment

Sometimes, finding the right "recipe" for the composition of the alloy and the way the metal is treated is critical to achieving the desired final properties. A good example is the shape memory properties of Nitinol - also known as NiTi or Nitinol.

The "elastic" material was first commonly used to make eyeglass frames that could bend and seemingly magically return to their original shape. NiTi is now widely used in medical device catheter applications such as catheter guides, stents and microsurgical needles.

You can find it in our white paper, Medical Device Tubing for the 21st Century: Who Needs It? For more information about NiTi and other piping materials.

The shape memory properties of NiTi depend on heat treatment. It is what enables NiTi to deform at one temperature and then return to its original undeformed shape when heated above its so-called transition temperature.

However, NiTi is notoriously difficult to manufacture due to the high reactivity of titanium and the fact that even small changes in composition can affect the conversion temperature.

For example, if titanium atoms combine with oxygen or carbon, the NiTi crystal structure loses titanium, resulting in a lower conversion temperature. If there is too little nickel and the material ages too long, the conversion temperature increases.

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