Researchers from Ruhr University Bochum, Germany, report that high-entropy shape-memory alloys have recently received significant scientific attention because they show how chemical complexity affects elementary characteristics such as phase stability, diffusion, and deformation behavior. They reported on this study at the ASM International SMST 2019 conference in Germany in a presentation titled “High Entropy Shape Memory Alloys – Effects of Chemical Complexity on Martensitic Transformation.”
A few years ago, a new compositionally complex shape memory alloy of type Ni-Cu-Co-Ti-Hf-Zr was introduced by G.S. Firstov and co-workers. This material, which is derived from binary Ni-Ti, shows a reversible martensitic transformation at elevated temperatures.
In the present study, the team investigated how chemical complexity affects the martensitic transformation in NiTi-based SMAs in terms of phase transformation temperatures, latent heats, cyclic stability, and microstructures. They considered Firstov-type high-entropy shape memory alloys (HESMAs) and SMAs with compositions from HESMA subsystems with lower configurational entropy.
The different SMAs were prepared by arc melting and subsequent heat treatments. The phase transformation behavior was characterized by differential scanning calorimetry. HESMA microstructures were characterized by scanning electron microscopy and electron probe micro analysis (EPMA). In the present work, they presented first results on the formation of martensite in chemically complex SMAs during in-situ cooling in a scanning electron microscope.
Authors: Mr. David Piorunek, Dr. Jan Frenzel, Prof. Gunther Eggeler , Ruhr University Bochum, Germany www.uaruhr.org/rub
SMST (Shape Memory and Superelastic Technologies) Conference and Exposition
May 13 – 17, 2019 at the Bodenseeforum in Konstanz, Germany.
https://www.asminternational.org/web/smst-2019
https://www.asminternational.org/web/smst/home
