>> The Shape Memory Alloys (SMA):

The shape memory alloys (SMA) gather metallic alloys with various properties:

. The superelasticity: the alloy can be bent in a reversible way under a constraint;

. The one-way memory effect: the alloy, after a mechanical bending, can find its initial shape back by a thermic evolution;

. The two-way memory effect: the alloy can, after "education", have two steady positions, one above a "critical" temperature and one below;

. The rubbery effect: the alloy, under bending, keeps, after relaxation, a residual bending; when the material is worked again, this residual bending increases;

. The damping effect: the alloy can absorb the shocks or reduce the mechanic vibrations.

These properties are essentially linked to a solid phase transformation during which a "mother phase" (austenite) leads, in a reversible crystallographic way, to a phase called martensite, it thus explains the name: "martensic transformation".

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