Which property do NiTi wires NOT possess?

Nickel-titanium (NiTi) wires are known for their unique properties, which include superelasticity and shape memory capabilities. The behavior of NiTi can be attributed to its ability to change its crystal structure in response to temperature and stress, thus facilitating both shape memory and superelastic effects. Superelasticity allows the material to undergo significant deformation and return to its original shape upon unloading, while shape memory enables the material to return to a pre-defined shape upon heating.

The correct answer highlights that NiTi wires do not possess poor shape memory. In fact, one of the defining characteristics of NiTi alloys is their excellent shape memory effect. This effect is utilized in various applications, such as in orthodontics and medical devices, where the wires can be activated by temperature changes. As a result, the misconception that NiTi wires have poor shape memory is fundamentally incorrect, as they are celebrated for their remarkable ability to retain and recover their shape effectively.

The other properties mentioned—superelasticity, the ability to exist in multiple crystal structures, and good shape memory—are well-established characteristics of NiTi alloys, underlining their versatility and unique behavior in various applications.