A shape-memory alloy is a metal that can be bent or deformed while cold and then made to spring back to an earlier, remembered shape simply by heating it, a property that comes from a reversible change between two crystal structures: a lower-temperature martensite phase, which deforms easily by rearranging its crystal twins rather than breaking atomic bonds, and a higher-temperature austenite phase, which the metal returns to on heating, pulling the deformed shape back with it. Shape-memory behavior in various alloys was observed as early as the 1930s and 1940s, but the alloy that made the effect practically useful, a nickel-titanium compound later marketed as Nitinol, was developed at the United States Naval Ordnance Laboratory in 1962 and 1963; according to the standard account, its shape-memory property was discovered by accident when a researcher held a lighter under a bent sample during a meeting and watched it straighten back out as it warmed. Nitinol and related shape-memory alloys are now used in applications including dental braces, medical stents, aircraft components and seismic bracing for buildings.
Facts
Patent or First-Use Date YearSourced to the subject's own account SignificanceSourced to the subject's own accountNitinol's shape-memory effect was dramatically demonstrated when a folded, accordion-like sample was passed around a 1961 laboratory management meeting and flexed by participants, the moment credited with making the effect practically recognized. 2 FAQs
How was the shape-memory effect of Nitinol first shown to its developers
A meeting demonstration in 1961: a folded sample straightened back out when a participant warmed it with a pipe lighter.
It was shown to a room of people. In 1961 researchers at the United States Naval Ordnance Laboratory presented a sample of the nickel-titanium alloy at a laboratory management meeting. The sample was folded up like an accordion and passed around, and the participants flexed it. One of them held the heat of a pipe lighter to the strip, and it contracted and took back its earlier shape. A year later the laboratory announced that it had successfully created Nitinol.
Connections
Associated With
Nitinol, Materials Nitinol, a nickel-titanium alloy, is the best known shape-memory alloy.
In Field
Source Shape-memory alloy (Wikipedia)
Sources
1. US Patent 3174851A, Nickel-base alloys
Abstract, opening sentence; publication date field shows 1965-03-23Quote, Abstract, opening sentence; publication date field shows 1965-03-23
This invention relates to a series of novel structural alloys of the intermetallic compound type which are characterized by unusual mechanical and physical properties.
2. Nitinol (Wikipedia)
WikipediaHistory section, NOL announcement sentence
One year later, the Naval Ordinance Lab announced the successful creation of nitinol.
History section, 1961 demonstration sentence
In 1961, they presented a sample at a laboratory management meeting. The sample, folded up like an accordion, was passed around and flexed by the participants.
View the Source Shape-memory alloy (Wikipedia)
In Field: Materials Engineering, IntroductionQuote, In Field: Materials Engineering, Introduction
In metallurgy, a shape-memory alloy (SMA) is an alloy that can be deformed when cold but returns to its pre-deformed ("remembered") shape when heated.
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