As per the literature available Shape memory and superelasticity are the two nature of nitinol SMA. Even though it is a superelastic alloy in nature still we call it as NiTi (nitinol) SMA (shape memory alloy).
Apart from phase transformations, are there any differences between the both?
There are two prominent SMAs based alloy which are Cu-Al-Ni and Nitinol that is Nickel- Titanium alloys. There are other Fe based and Cu based SMAs which are commercially available. So to ask of differences between Nitinol and SMA, in my opinion I will say Nitinol is SMA based alloy so nothing to distinguish. We can make comparison with Nitinol and other SMAs based alloy.
Dear seun , can you clarify something about superelasticity and shape memory property of Nickel Titanium alloys ? In terms of properties and applications ?
Dear Vinayak,
the difference are phase transformation temperatures. The superelastic one at room temperature is in austenitic phase during deformation forms martensite and when applied load is removed it transforms back to austenite and shape recovery occurs. Shape memory one at room temperature is in martenisic phase when deformed martensite is twinned and during heating above austenite start temperature its shape is recovered. The difference of phase transformation temperatures is caused by different chemical composition take a look at the image in the link:
https://upload.wikimedia.org/wikipedia/commons/thumb/0/0f/Nitinol_Ms_vs_Ni_content.jpg/440px-Nitinol_Ms_vs_Ni_content.jpg
Hello Vinayak,
SHAPE MEMORY Alloy posses two properties
Superelasticity
shape emeory effect
Based on the initial or working temperature of shape memory alloy.
when the SMA temperature is below Mf(martensite finish temperature), then it posses SME
if the temperature is above Aof( aUSTENITE FINISH TEMPERATURE), IT POSSES superelasticity.
I am attaching one book see it
Dear vinayak
Superelasticity is the material which is in austenite phase at room temperature during loading, when unloaded deforms back to its original shape.
Shape memory effect can be understood by the material in martensite twinned phase at room temperature. When loaded deforms to detwinned and when unloaded i.e. cheated recovers all the stresses and deforms back to its original shape
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