CAREER: Interface Deformation and Compatibility in Shape Memory Polycrystals

Rensselaer Polytechnic Institute, Troy NY

Investigators

Abstract

Technical Summary: Shape Memory Alloys (SMAs) are unique multifunctional phase-change materials. They can switch between two shapes under thermal or mechanical cycling by a reversible martensitic phase transformation, and are promising for applications in sensing, actuation, energy conversion and harvesting, and damping. This CAREER project bridges two thus far separate research areas, (i) grain boundary science and engineering and (ii) displacive martensitic transformations in SMAs, and seeks to understand mechanical interactions across interfaces during martensitic transformations in dual-phase SMA polycrystals. This research will use experiments, analytical theory, and mesoscale computational modeling to explore two major interface effects: (1) the effects of grain boundary crystallographic character on strain transfer, accommodation, and compatibility at grain boundaries; (2) how a non-transforming, ductile phase precipitated along grain boundaries accommodates transformation strains from across phase boundaries. Grain boundary engineering will be explored to enhance strain compatibility at grain boundaries, thereby improving the ductility and applicability of SMA polycrystals. The fundamental understanding on strain transfer and compatibility at interfaces gained in this research will also be relevant to similar problems in many other polycrystalline metals and compounds. Non-Technical Summary: Shape Memory Alloys (SMAs)are unique multifunctional materials. They can fail by brittle fracture along internal planar defects or interfaces called grain boundaries and this problem has significantly limited their applicability. This project will quantitatively elucidate the mechanisms for failure in SMAs by performing experimental characterizations and computational modeling. This work will also exploit grain boundary engineering strategies to improve grain boundary properties and enhance the ductility of SMAs, which will enable practical applications of SMAs in advanced technologies in both commercial and military sectors. This project will also involve substantial education and outreach efforts. The education activities include transforming both undergraduate and graduate core mechanical properties courses, contributing to computational materials course, and training undergraduate and graduate researchers who will become experts and leaders in mechanical properties, metals, and computational materials science. The outreach activities will attract young students to science and engineering, promote public interest in engineering, and support professional development and advancement of women engineering students.