1 Design of a V-Ti-Ni alloy with superelastic nano-precipitates J.-L. Zhang a,b,& , J.L. Cann a,& , S.B. Maisel b , K. Qu c , E. Plancher a,d , H. Springer b,e , E. Povoden- Karadeniz f , P. Gao c , Y. Ren g , B. Grabowski h , C.C. Tasan a,* a Dept. of Materials Science and Engineering, Massachusetts Institute of Technology, 77 Mass. Avenue, Cambridge, MA 02139 USA b Max-Planck-Institut für Eisenforschung GmbH, Max-Planck-Straße 1, 40237 Düsseldorf, Germany c International Center for Quantum Materials and Electron Microscopy Laboratory, School of Physics, Peking University, Beijing, 100871, China d Université Grenoble Alpes, CNRS UMR5266, Grenoble INP, Laboratoire SIMaP, 38000 Grenoble, France e Institute of Metal Forming, RWTH Aachen University, 52056 Aachen, Germany f Christian Doppler Laboratory for Interfaces and Precipitation Engineering CDL-IPE TU Wien, Vienna, Austria g X-Ray Science Division, Argonne National Laboratory, Lemont, USA h Institute of Materials Science, University of Stuttgart, Pfaffenwaldring 55, 70569 Stuttgart, Germany & Equal contribution, * Corresponding author Abstract Stress-induced martensitic transformations enable metastable alloys to exhibit enhanced strain hardening capacity, leading to improved formability and toughness. As is well-known from transformation-induced plasticity (TRIP) steels, however, the resulting martensite can limit ductility and fatigue life due to its intrinsic brittleness. In this work, we explore an alloy design strategy that utilizes stress-induced martensitic transformations but does not retain the martensite phase. This strategy is based on the introduction of superelastic nano-precipitates, which exhibit reverse transformation after initial stress-induced forward transformation. To this end, utilizing ab-initio simulations and thermodynamic calculations we designed and produced a V45Ti30Ni25 (at%) alloy. In this alloy, TiNi is present as nano-precipitates uniformly distributed within a ductile V-rich base-centered cubic (bcc) β matrix, as well as being present as a larger matrix phase. We characterized the microstructure of the produced alloy using various scanning electron microscopy (SEM) and transmission electron microscopy (TEM) methods. The bulk mechanical properties of the alloy are demonstrated through tensile tests, and the reversible transformation in each of the TiNi morphologies were confirmed by in-situ TEM micro-pillar compression experiments, in-situ high-energy diffraction synchrotron cyclic tensile tests, indentation experiments, and differential scanning calorimetry experiments. The observed transformation pathways and variables impacting phase stability are critically discussed Keywords: martensitic phase transformation; shape memory; NiTi; nanoparticles; in situ
Design of a V-Ti-Ni alloy with superelastic nano-precipitates
Jun 29, 2023
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