An alloy that retains its memory at high temperatures

December 03, 2019

Using computer simulation, Alberto Ferrari calculated a design proposal for a shape memory alloy that retains its efficiency for a long time even at high temperatures. Alexander Paulsen manufactured it and experimentally confirmed the prediction. The alloy of titanium, tantalum and scandium is more than just a new high-temperature shape memory alloy. Rather, the research team from the Interdisciplinary Centre for Advanced Materials Simulation (Icams) and the Institute for Materials at Ruhr-Universität Bochum (RUB) has also demonstrated how theoretical predictions can be used to produce new materials more quickly. The group published its report in the journal Physical Review Materials from 21 October 2019. Their work was showcased as Editor's suggestion.

Avoiding the unwanted phase

Shape memory alloys can re-establish their original shape after deformation when the temperature changes. This phenomenon is based on a transformation of the crystal lattice in which the atoms of the metals are arranged. Researchers refer to is as phase transformation. "In addition to the desired phases, there are also others that form permanently and considerably weaken or even completely destroy the shape memory effect," explains Dr. Jan Frenzel from the Institute for Materials. The so-called omega phase occurs at a specific temperature, depending on the composition of the material. To date, many shape memory alloys for the high temperature range would withstand only a few deformations before they became unusable once the omega phase set in.

Promising shape memory alloys for high temperature applications are based on a mixture of titanium and tantalum. By changing the proportions of these metals in the alloy, researchers can determine the temperature at which the omega phase occurs. "However, while we can move this temperature upward, the temperature of the desired phase transformation is unfortunately lowered in the process," says Jan Frenzel.

Admixture alters properties

The RUB researchers attempted to understand the mechanisms of the onset of the omega phase in detail, in order to find ways to improve the performance of shape memory alloys for the high-temperature range. To this end, Alberto Ferrari, PhD researcher at Icams, calculated the stability of the respective phases as a function of temperature for different compositions of titanium and tantalum. "He was able to use it to confirm the results of experiments," points out Dr. Jutta Rogal from Icams.

In the next step, Alberto Ferrari simulated small amounts of third elements being added to the shape memory alloy of titanium and tantalum. He selected the candidates according to specific criteria, for example they should be as non-toxic as possible. It emerged that an admixture of a few percent of scandium would have to result in the alloy functioning for a long time even at high temperatures. "Even though scandium belongs to the rare earths and is, consequently, expensive, we only need very little of it, which is why it's worth using anyway", explains Jan Frenzel.

Prediction is accurate

Alexander Paulsen then produced the alloy calculated by Alberto Ferrari at the Institute for Materials and tested its properties in an experiment: the results confirmed the calculations. A microscopic examination of the samples later proved that even after many deformations no omega phase was found in the crystal lattice of the alloy. "We have thus expanded our basic knowledge of titanium-based shape memory alloys and developed possible new high-temperature shape memory alloys," says Jan Frenzel. "Moreover, it's great that the computer simulation predictions are so accurate." Since the production of such alloys is very complex, the implementation of computer-aided design proposals for new materials promises much faster success.
-end-
Funding

The research was funded by the German Research Foundation as part of research group 1766 (project no. 200999873). Some of the calculations were performed using supercomputers by the Swedish National Infrastructure for Computing at National Supercomputer Centre (NSC) in Linköping and at the Center for High Performance Computing in Stockholm.

Original publication

Alberto Ferrari, Alexander Paulsen, Dennis Langenkämper, David Piorunek, Christoph Somsen, Jan Frenzel, Jutta Rogal, Gunther Eggeler, Ralf Drautz: Discovery of ω-free high-temperature Ti-Ta-X shape memory alloys from first-principles calculations, in: Physical Review Materials 2019, DOI: 10.1103/PhysRevMaterials.3.103605

Press contact

Dr. Jutta Rogal
Atomistic simulation of the kinetics of phase transformations
Interdisciplinary Centre for Advanced Materials Simulation
Ruhr-Universität Bochum
Phone: +49 234 32 29317
Email: jutta.rogal@rub.de

Dr. Jan Frenzel
Chair for Materials Science and Engineering
Institute for Materials
Department of Mechanical Engineering
Ruhr-Universität Bochum
Phone: +49 234 32 22547
Email: jan.frenzel@rub.de

Ruhr-University Bochum

Related Titanium Articles from Brightsurf:

A 40-year-old catalyst unveils its secrets
Activity of the industrial catalyst TS-1 relies on titanium pairs / important discovery for catalyst development

Direct observation of a single electron's butterfly-shaped distribution in titanium oxide
A research team led by Nagoya University has observed the smeared-out spatial distribution of a single valence electron at the centre of a titanium oxide molecule, using synchrotron X-ray diffraction and a new Fourier synthesis method also developed by the team.

Titanium oxide-based hybrid materials promising for detoxifying dyes
Photoactive materials have become extremely popular in a large variety of applications in the fields of photocatalytic degradation of pollutants, water splitting, organic synthesis, photoreduction of carbon dioxide, and others.

Scientists have created new nanocomposite from gold and titanium oxide
ITMO University researchers together with their colleagues from France and the USA have demonstrated how a femtosecond laser can be used to tune the structure and nanocomposite properties for titanium dioxide films filled with gold nanoparticles.

Skoltech scientists developed a new cathode material for metal-ion batteries
Researchers from the Skoltech Center for Energy Science and Technology (CEST) created a new cathode material based on titanium fluoride phosphate, which enabled achieving superior energy performance and stable operation at high discharge currents.

First view of hydrogen at the metal-to-metal hydride interface
University of Groningen physicists have visualized hydrogen at the titanium/titanium hydride interface using a transmission electron microscope.

The properties of thin titanium oxide films have been studied
Some titanium oxides are known for their unique properties, such as increased photocatalytic activity (i.e. they effectively use light to speed up chemical reactions).

Adding copper strengthens 3D-printed titanium
Successful trials of titanium-copper alloys for 3D printing could kickstart a new range of high-performance alloys for medical device, defence and aerospace applications.

Fatigue-resistant, high-performance cooling materials enabled by 3D printing
High-performance solid-state elastocaloric cooling materials with exceptional fatigue resistance are made possible by 3D printing a nickel-titanium based alloy, researchers report.

Common food additive found to affect gut microbiota
Experts call for better regulation of a common additive in foods and medicine, as research reveals it can impact the gut microbiota and contribute to inflammation in the colon, which could trigger diseases such as inflammatory bowel diseases and colorectal cancer.

Read More: Titanium News and Titanium Current Events
Brightsurf.com is a participant in the Amazon Services LLC Associates Program, an affiliate advertising program designed to provide a means for sites to earn advertising fees by advertising and linking to Amazon.com.