What are shape memory alloys?

Shape Memory Alloys A shape-memory alloy is an alloy that "remembers" its original, cold-forged shape: returning the pre-deformed shape by heating. Shape Memory Alloys (SMAs) are a unique class of metal alloys that can recover apparent permanent strains when they are heated above a certain temperature.

Shape Memory Effect

MfMf MsMs AsAs AfAf AusteniteMartensite TEMPERATURE MfMf MsMs AsAs AfAf AusteniteMartensite TEMPERATURE (twinned)

Shape Memory Effect TEMPERATURE STRESS MfMf MsMs AsAs AfAf TEMPERATURE STRESS MfMf MsMs AsAs AfAf Twinned Martensite (unstressed) Detwinned Martensite (stressed - deformed) Detwinned Martensite (unstressed - deformed) Austenite (undeformed)

Pseudo/Super Elasticity

History A. Ölander discovered the pseudoelastic behavior of the Au-Cd alloy in Greninger and Mooradian (1938) observed the formation and disappearance of a martensitic phase by decreasing and increasing the temperature of a Cu-Zn alloy. The basic phenomenon of the memory effect governed by the thermoelastic behavior of the martensite phase was widely reported a decade later by Kurdjumov and Khandros (1949) and also by Chang and Read (1951).

Nitinol Discovery The nickel-titanium alloys were first developed in 1962–1963 by the United States Naval Ordnance Laboratories and commercialized under the trade name Nitinol. Later Ferromagnetic Shape Memory Alloys were also discovered.

Nitinol Crystal Structure

Economic Failures in Nitinol

Applications

Solder Applications

Helicopter Actuator System

Interesting Future applications

How is it possible?

A Jelly Fish Robot

Trending Branches of Research Porous SMA Shape Memory Polymers Iron Based SMA Ferromagnetic SMA Shape Memory Composites Shape Memory Hybrids Magnetic Shape Memory Materials High Temperature Ni-Ti-Pt alloys Synthesis by P/M route

So do keep in memory these memory materials with wonderful memories. and

References Dictionary.com Wikipedia.com Shape Memory Alloys by Darel E. Hodgson, Shape Memory Applications, Inc., Ming H. Wu, Memry Corporation INDUSTRIAL APPLICATIONS FOR SHAPE MEMORY ALLOYS Ming H. Wu and L. McD. Schetky Memry Corporation, 57 Commerce Drive, Brookfield, Connecticut) Shape memory alloys from active materials lab.