报告题目：Fundamentals and Applications of Ambient and High-Temperature Shape Memory Alloys
报告人：Prof. Peter M. Anderson, Professor and department chair, Materials Sci. & Eng.，The Ohio State University, Ohio, USA
Peter M Anderson is Professor and Chair in the Department of Materials Science and Engineering at The Ohio State University. He received his PhD in Engineering Sciences at Harvard University and was a Post-doc in the Engineering Department at University of Cambridge (UK). His work pursues the relationships between mechanical properties and underlying material structure. Applications include “quantized crystal plasticity” in nanograined metals, concepts of strengthening and work hardening in nanolayered composites, the development of nanoindentation techniques to extract size-dependent strength in nanostructured composites, novel finite element-phase field simulations, the development of wear-resistant materials that employ phase transformations, and the design of biological scaffolds that can aid in cell differentiation and growth. He is a coauthor of the new (3rd) edition of Theory of Dislocations, released in February 2017 (coauthored with John Hirth and Jens Lothe).
Shape memory alloys (SMAs) offer the potential for a vast array of applications, including actuators for reconfigurable blades on rotorcrafts, variable geometry chevrons on aircraft engines, flap actuators on aircraft wings, and even shape-changing bio-inspired structures. However, there are considerable challenges that include functional and structural fatigue under repeated actuation. Understanding these phenomena is critical to the design and application of new high temperature SMAs for automotive and turbine engine applications.
This talk focuses on the coupling of phase transformations and plastic deformation in SMAs at the micro- and nano- structural scale. Amazingly, dislocation patterns develop during heating/cooling of NiTi SMAs, even in the absence of macroscopic loads. In new high temperature Ni-Ti-Hf SMAs, nanoscale precipitates effectively suppress plasticity during heating/cooling without impeding the phase transformation. Recent phase field-finite element simulations are used to study the origins of dislocation patterning during transformations, and how nanoscale precipitates and plasticity can serve as templates for patterning of martensite. This work is supported by the US Department of Energy/Basic Energy Sciences.