October_AMP_Digital

A D V A N C E D M A T E R I A L S & P R O C E S S E S | O C T O B E R 2 0 2 0 4 1 Shape Memory and Super- elasticity: Advances in Science and Technology ( SMJ ) is the offi- cial journal of the International Organization on Shape Memory and Superelastic Technologies (SMST), an affiliate society of ASM International. The jour- nal publishes original peer- reviewed papers that focus on shape memory materials re- search with contributions from materials science, experimental and theoretical mechanics, physics with cognizance of the chemistry, underlying phases, and crystallography. It also provides a forum for researchers, scientists, and engineers of varied disciplines to access in- formation about shape memory materials. The four articles described here are from the June issue, which contained papers honoring Professor Gunther Eggeler for 25 years of shape memory research. All were selected by Shape Memory Editor-in-Chief Huseyin Sehitoglu. SMJ is available through springerlink.com. For more information, visit asminternational. org/web/smst. THE EFFECT OF INCREASING CHEMICAL COMPLEXITY ON THE MECHANICAL AND FUNCTIONAL BEHAVIOR OF NiTi-RELATED SHAPE MEMORY ALLOYS Christian Hinte, Khemais Barienti, Jan Steinbrücker, Jana-Mercedes Hartmann, Gregory Gerstein, Sebastian Herbst, David Piorunek, Jan Frenzel, Andrea Fantin, and Hans Jürgen Maier The introduction of high-entropy alloys (HEA) into the field of shape memory alloys offers enormous potential for improving their functional properties. It is shown how a suc- cessive increase in chemical complexity results in strictly monotonically enlarged and increasingly distorted lattices. With increasing the number of elements added to the alloy, the effect of solid solution strengthening appears to be curtailed and first insights into the contribution of additional mecha- nisms based on lattice distortions are possible. The alloys de- veloped in this study, reaching from ternary NiTiHf to senary TiZrHfCoNiCu, show a great potential to exploit interatomic interactions regarding improvement of functional fatigue. Despite the absence of stress plateaus related to detwinning, recovery effects at loads above 1000 MPa and significant strain recoveries are shown (Fig. 1). DSC CYCLING EFFECTS ON PHASE TRANSFORMA- TION TEMPERATURES OF MICRON AND SUBMICRON GRAIN Ni 50.8 Ti 49.2 MICROWIRES Saeid Pourbabak, Bert Verlinden, Jan Van Humbeeck, and Dominique Schryvers The effect of thermal cycling parameters on the phase transformation temperatures of micron and submicron grain size recrystallized Ni–Ti microwires was investigated. The sup- pression of martensitic transformation by thermal cycling was found to enhance when combined with room temperature ag- ing between the cycles and enhances evenmore when aged at elevated temperature of 100°C. While aging at room tempera- ture alone has no clear effect on the martensitic transforma- tion, elevated temperature aging at 100°C alone suppresses the martensitic transformation. All aforementioned effects were found to be stronger in large grain samples than in small grain samples. Martensitic transformation suppression in all cases was in line with the formation of Ni 4 Ti 3 precursors in the SMJ HIGHLIGHTS Fig. 1 — Excerpt from the periodic table of elements; alloy systems investigated by the different research groups are highlighted by the respective color. Fig. 2 — DSC results of the LEC sample tested at different days and aged at 100°C in between. 1 1