A shape memory alloy or SMA is a kind of an alloy which ‘remembers’
2. Ni-Ti shape memory alloy
A Ni-Ti shape memory alloy is a type of a memory alloy which has nickel and titanium as its constituent metals. These elements are mixed in roughly the same amounts to make this alloy. Ni-Ti shape memory alloy is one of the most common or popular SMA because it is more practical to use, is more stable and has excellent thermo-mechanic performance as compared to certain other elements or alloys.
3. Obtaining Ni-Ti shape memory alloy
Ni-Ti shape memory alloy is commonly referred to as nitinol and it is quite difficult to make. An exceptionally tight compositional control is needed to form this alloy and due to the exceptionally high reactivity of titanium metal, this process becomes tough. The following are the two methods using which nitinol can be obtained:
· Vacuum Arc Remelting- In this melting method, an electrical arc is striked between the raw material and the water-cooled copper strike plate. This process is observed or performed in a high vacuum and even the mold used is water-cooled copper. There is no need for carbon to be introduced during Vacuum Arc Remelting process.
· Vacuum induction melting- This is a method to makenitinol which is observed by making use of alternative magnetic fields to heat the raw materials in a crucible. This process is performed by high vacuum and carbon is introduced during the process.
4. The composition
Component 1: Titanium
Titanium is a transition metal with atomic number 22 and symbol Ti. This metal appears lustrous and was discovered in the year 1791. Since titanium metal is not found in its isolated state, it has to be extracted from its mineral ores. It occurs within mineral deposits found in all living things including soils, rocks and water bodies etc. The primary ores of titanium metal are rutile and ilmenite. The extraction process which is used to obtain titanium is called Kroll or Hunter process.
Component 2: Nickel
Nickel is a chemical element with atomic number 28 and chemical symbol Ni. This element appears to be silvery white and it too is lustrous like titanium. It also has a slight golden tinge and is a hard and ductile metal. Nickel falls in the category of transition metals and it was first isolated and identified as an element in the year 1751. This is a corrosion resistant chemical element because it has a slow rate of oxidation and room temperature. Nickel is often used as a constituent of many alloys such as the Ni-Ti shape memory alloy.
Other shape memory alloys
Besides Ni-Ti shape memory alloy, there are two other main types of memory alloys which are copper-zinc-
By Stanford Advanced Materials http://www.samaterials.com/
Stanford Advanced Materials (SAM) Corporation is a global supplier of a series of pure metals, alloys, ceramics and minerals such as oxides, chlorides, sulfides, oxysalts, etc. Our headquarter, located in Irvine, California, USA, was first established in 1994, starting to provide high-quality rare-earth products for research and development (R&D).
Stanford Advanced Materials
Stanford Advanced Materials