Nickel-titanium alloy or simply nickel titanium is also popularly known as Nitinol. It is composed of those two elements at almost equal atomic proportions. It is one of the most useful alloys used for numerous purposes, especially essential medical applications. Nitinol shows super elasticity and shape memory properties, meaning it can remember its original shape and demonstrates great elasticity under stress.
In terms of its basic physical and mechanical properties, Nitinol has an appearance of bright silvery metal and has a density of 6.45 gm/cm3. When it comes to its melting point, nickel titanium melts at around 1310 °C and it can resist about 82 ohm-cm of higher temperatures and 76 ohm-cm of lower temperatures. As for its thermal conductivity, Nitinol has it at 0.1 W/ cm-°C. In order to produce this amazing alloy, very tight compositional control is needed, making its production quite difficult. In addition, the high reactivity of titanium, which makes its preparation even more challenging.
There are two major methods in melting the raw materials for producing nickel titanium. One is through the Vacuum Arc Remelting method, wherein an electrical arc is struck between water-cooled copper strike-plate and the elements. During the melting process, a water-cooled copper mold is used to melt the constituents in a high vacuum to avoid introducing carbon to the materials. The second method is called the Vacuum Induction Melting, in which the ingredients are being heated in a carbon crucible with the use of alternating magnetic fields. This process is also done using a high vacuum but carbon is introduced in this method.
Both of these methods have their own pros and cons and have varying advantages to offer. There are other methods that can also be used such as plasma arc melting, e-beam melting, induction skull melting, physical vapor deposition, and more, depending on the specific purpose.
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