About ElastaMet and Single Crystal Shape Memory Alloys (SCSMAs)
Produced using a proprietary version of the Stepanov crystal growing method, these uniform monocrystaline Copper-Aluminum alloys have these amazing abilities:
Incredible flexibility - Up to nine percent "hyper elastic" deformation with full recovery (eighteen times greater than stainless steel)
Constant force deflection - Steady force exerted along nearly the entire deformation range
High spring energy storage - Twenty times greater per unit mass than stainless steel. Store twenty times the energy in the same mass, or reduce the mass of the spring element to 1/20th. Traditionally, any "order of magnitude" change in technology brings forth entirely new possibilities.
Biocompatible - Preliminary tests show ElastaMet alloys to have no adverse biological effects in either cell cytotoxicity or systemic toxicity tests. Further tests are ongoing.
Precise temperature transition - As with other shape memory alloys, the ratio of component alloys determines the the initial Af transition temperature. But with ElastaMet and our proprietary post-alloying process, we can actually "dial up" an exact Af temperature. This permits wide new array of new temperature specific devices demanding high performance and high reliability.
Solderable - The copper-based ElastaMet alloys accept a range of specialized solders when used with appropriate fluxes. Using low-temperature solders best protects the alloy from overheating. Other methods of joining such as welding and laser welding can also work.
Single crystal SMA is generally fabricated using a special procedure known as the Stepanov method.
A "seed crystal" of the desired alloy is lowered into a crucible containing a melted ingot of the alloy composition, and gradually drawn up. Surface tension pulls the melted metal along with the seed.
The rising column cools as it leaves the surface of the melt. The rate of drawing is controlled to correspond with the rate of cooling so that a solid crystal is formed at a region that becomes a crystallization front. This front remains stationary while the crystal, liquid below and solid above, travels through it.
The top surface of the melt can contain a die (of the desired cross-sectional shape) that forms the shape of the crystal as it grows.
Since conventional hot or cold mechanical processing (rolling, wire drawing, etc.) destroy ElastaMet's uniform single crystal structure, special procedures must be used.
Parts can be formed nearly to desired shape directly from the melted alloy. Rods, bars, tubes and other shapes can be made, from a few millimeters up to and over 1 centimeter across. Due to the surface tension of the molten alloy, all parts have slightly rounded corners.
Pulled shapes can be easily machined using traditional cutting, drilling, grinding and other methods, as long as the ElastaMet alloy is not overheated (conventional cooling methods are usually sufficient). Overheating can change the ElastaMet crystal's properties and reduce or destroy its performance.
Extremely intricate shapes can be formed using wire EDM (Electrical Discharge Machining which works by eroding the material using small electrical discharges). Some useful information on EDM can be found here
ElastaMet can be finished using using mechanical polishing, as well as electropolishing, which leaves the material with a bright copper-like finish. Other finishes and processes may also apply. Contact us with your needs.
Shape Memory Effects
Since ElastaMet belongs to the family of Shape Memory Alloys (SMAs) - metals that have widely varying flexibility on either side of a distinct transition temperature, such as Nitinol - ElastaMet alloys also exhibit amazing temperature-activated shape recovery abilities.
ElastaMet has many benefits and abilities not found in other SMAs:
Wider transition temperature range - By varying the ratio of the component metals, ElastaMet alloys can be produced having an Austenite finish (Af) transition temperature anywhere in the range of minus 150 degrees C to over 250 degrees C - a range two times greater than Nitinol.
Very narrow loading / unloading hysteresis
Very low resistivity - Copper-based ElastaMet is an excellent conductor, making it ideal for electrical contacts that must tolerate extensive flexing. However, unlike Nitinol alloys, ElastaMet does not heat easily due to resistive heating, and thus external thermal heating is preferred to activate the shape memory effects.
Full shape recovery that is repeatable and complete even at a nine percent deformation (three times that of Nitinol, and eighteen times greater than stainless steel). This means that a 6mm diameter ElastaMet rod can be bent into a "U" shape with a diameter of about 60mm, and it will return fully to its starting shape when released.
For more technical details visit our resources page.
Or click here to order an ElastaMet Sample Kit.
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