Metal foam has a good memory(egree of strain. The researchers created...)

The researchers created the new material by pouring molten alloy into a piece of porous sodium aluminate salt. Once the material cooled, they leached out the salt with acid, leaving behind large voids. The researchers then exposed the porous alloy to a rotating magnetic field. The level of strain achieved after each of the over 10 million rotations is consistent with the best currently used magnetic actuators, and Mllner and Dunand expect to significantly improve the strain when they have further optimized the foam's architecture.

"The base alloy material was previously known, but it wasn't very effective for shape-memory applications," Dunand said. "The porous nature of the material amplifies the shape-change effect, making it a good candidate for tiny motion control devices or biomedical pumps without moving parts." NSF Program Director Harsh Deep Chopra agrees. "It's the first foam to exhibit magnetic shape memory - it has great potential for uses that require a large strain and light weight such as space applications and automobiles. These materials are able to do more with less material given their foamy structure and provide a sustainable approach to materials development."

The work was funded by NSF through grant DMR-0502551 to expand basic knowledge about the microstructural properties of shape memory alloys influenced by magnetic fields and through grant DMR-0505772 to develop new shape-memory foams.