#superelasticity

Researchers at Tohoku University have developed a groundbreaking titanium-aluminum (Ti-Al)-based superelastic alloy. This new material is not only lightweight but also strong, offering the unique superelastic capability to function across a broad temperature range -- from as low as -269°C, the temperature of liquid helium, to +127°C, which is above the boiling point of water. This discovery holds significant potential for a variety of applications, including those in space exploration and medical technology. Sheng Xu, an Assistant Professor at Tohoku University's Frontier Research Institute for Interdisciplinary Sciences, emphasized the importance of the alloy's wide operational temperature range. "This alloy is the first of its kind to maintain superelasticity at such an extreme range of temperatures while remaining lightweight and strong, which opens up a variety of practical applications that were not possible before. The alloy's properties make it ideal for future space missions, such as creating superelastic tires for lunar rovers to navigate the extreme temperature fluctuations on the Moon's surface."

Scientists achieve giant magneto-superelasticity in metal crystal

Recently, a research group developed a giant magneto-superelasticity of 5% in a Ni34Co8Cu8Mn36Ga14 single crystal. This was achieved by introducing arrays of ordered dislocations to form preferentially oriented martensitic variants during the magnetically induced reverse martensitic transformation. The research was published in Advanced Science. Elasticity is the ability of materials to return to their original shape after deformation, typically with a strain of 0.2% in most metals. Shape memory and high entropy alloys can exhibit superelasticity with strains of several percent, usually triggered by external stresses. Magneto-superelasticity, induced by a magnetic field, is crucial for contactless material operation and the development of new large stroke actuators and efficient energy transducers.

The compound of iron and aluminum with the chemical formula Fe3Al has some very useful mechanical properties. A team from Osaka University has combined simulations with experimental techniques to better understand the kinetics of the formation of microstructures to enhance and utilize these properties and how to harness them for specific applications. In a study recently published in Acta Materialia, the researchers took an in-depth look at the way the microstructure of Fe3Al develops because the ordered domains that form contribute to one of its key properties: superelasticity. When high loads are applied to superelastic materials they can deform to large strains which would result in a permanent strain in conventional materials without break. Interestingly, they can return to their original shape when unload. This can be used in a diverse range of applications from healthcare materials seismic devices for construction materials.

New flexible and tough superelastic metal alloy shows promise in biomedical applications

A research group has revealed a cobalt-chromium-based biomaterial that mimics the flexibility of human bones and possesses excellent wear resistance. The new biomaterial could be used for implants such as hip or knee joint replacements and bone plates, alleviating problems associated with conventional implant materials.

Details of their research were published in the journal Advanced Materials on May 9, 2022.

With the elderly population increasing across the globe, the need for improved biomaterials that can replace or support damaged bones has risen. For this purpose, metals are widely used because of their strength and ductility. However, as a consequence of their strength, their flexibility diminishes.

To date, most metallic biomaterials are stiffer than human bones, and using them as implants leads to bone atrophy—a condition where bone density is reduced because of a breakdown in bone substance and structure. Meanwhile, biomaterials with elevated flexibility lose their wear resistance.

New aerogel maintains functionality, superelasticity at extreme temperatures

Aerogel materials serve a vital role as protective materials needed for many fields, including as electromagnetic interference shielding material for 5G technology, thermally insulating material in high-rise buildings and infrared stealth material for military applications. Current protective materials, however, often lose their protective functions under harsh conditions such as extreme temperatures, rendering them ineffective. Other protective materials lose their elasticity, leading to similar performance issues. Now, new aerogel materials that can maintain their functionality and superelasticity under extreme temperatures have been developed by a team of researchers from Sichuan University.

The results were published in Nano Research.

"We aimed to solve the problem that the performance of conventional protective aerogel materials deteriorates severely under harsh working conditions," said corresponding author Hai-Bo Zhao, professor in the College of Chemistry at Sichuan University.

Researchers develop 3D-printed shape memory alloy with superior superelasticity

Laser powder bed fusion, a 3D-printing technique, offers potential in the manufacturing industry, particularly when fabricating nickel-titanium shape memory alloys with complex geometries. Although this manufacturing technique is attractive for applications in the biomedical and aerospace fields, it has rarely showcased the superelasticity required for specific applications using nickel-titanium shape memory alloys. Defects generated and changes imposed onto the material during the 3D-printing process prevented the superelasticity from appearing in 3D-printed nickel-titanium.

Researchers from Texas A&M University recently showcased superior tensile superelasticity by fabricating a shape memory alloy through laser powder bed fusion, nearly doubling the maximum superelasticity reported in literature for 3D printing.

This study was recently published in vol. 229 of the Acta Materialia journal.  

Nickel-titanium shape memory alloys have various applications due to their ability to return to their original shape upon heating or upon removal of the applied stress. Therefore, they can be used in biomedical and aerospace fields for stents, implants, surgical devices and aircraft wings. However, developing and properly fabricating these materials requires extensive research to characterize functional properties and examine the microstructure.

Superelasticity of a photoactuating chiral crystal

Superelasticity is an elastic response to an applied external force that occurs via phase transformation. The resulting actuation of the materials is an elastic response to external stimuli, including light and heat. While superelasticity and actuation are deformations resulting from stimulus-induced stress—a phenomenological difference exists between the two, depending on the force. In a new report now published in Communications Chemistry, Takuya Taniguchi and a research team in advanced science and engineering, data science, life sciences and materials science in Japan, described a molecular crystal that manifested superelasticity during photo-actuation under light irradiation. The crystal showed step-wise twisted actuation based on two effects, including photoisomerization and photo-triggered phase transition. They simulated the actuation behavior on a dynamic multi-layer model to reveal progressive photoisomerization and phase-transition in the crystal, while indicating superelasticity induced by modest stress as a result of photoproduct formation. The work provides successful simulations of step-wise twisted actuation to indicate superelasticity-induced by light.

A superelastic alloy with a nearly limitless temperature window

A team of researchers at Tohoku University has developed a new kind of superelastic alloy with a nearly limitless superelastic window. In their paper published in the journal Science, the group describes the new alloy's properties and possible uses for it. Paulo La Roca and Marcos Sade with Universidad Nacional de Cuyo–CNEA have published a Perspective piece in the same journal issue outlining the state of bendable alloys and the work done by the team in Japan.

Most metals in everyday use can bend somewhat. To get them to return to their original shape generally requires force such as from a hammer. Superelastic alloys (also known as metals with shape memory) can be bent with up to 20 percent deformations and will return to their original shape automatically. La Roca and Sade note that superelasticity in metals can be explained by the presence of stress-induced martensitic transformations. But there is a caveat for such alloys—they can only rebound back to their original shape when they are in a certain range of temperatures: their superelastic window.