Switchable multiferroics are a class of advanced materials with distinct elastic, electric, and magnetic properties that can be “switched on or off” through reversible martensitic phase transformations. In layman’s terms: heating or cooling and/or applying a pressure change to these materials will (reversibly) cause a rearrangement of their atomic structures and give them properties they would not otherwise have, such as being or not being magnetic. These are referred to as solid-solid martensitic phase transformations, as the materials change from one solid arrangement to another and not to a liquid or to a gas.
Martensitic phase transformations enable many diverse materials, including shape memory alloys, high-entropy alloys, superconductors, steels, elastomers, and many materials at high strain rates, to perform surprising feats necessary for advanced solid-state technologies. However, the longstanding challenge associated with reversible martensitic phase transformations is that they tend to not actually be reversible in practice. They exhibit functional fatigue (i.e., changes to the material response during cyclic loading that diminish its exploitative properties), which limits the life cycle of these materials and, thus, the advanced technologies that depend on them.
Ashley Bucsek, Assistant Professor of Mechanical Engineering, has been awarded a 2022 NSF CAREER Award for her proposal and work on martensitic phase transformations. Her proposal, titled “Understanding the Origins of Mechanical Hysteresis and Functional Fatigue in Martensitic Phase Transforming Materials,” seeks to understand why and how materials degrade, after repeated martensitic phase transformations.
According to recommendations made by the National Academies for U.S. materials and manufacturing research investments for 2020–2030, understanding the fundamental mechanics of advanced materials using new experimental tools is critical for the deployment of urgent new technologies. As described above, the degradations of advanced materials, which Dr. Bucsek will study, are important to understand for the development of just such urgent new technologies prioritized by the National Academies.
In more specific terms, Dr. Bucsek seeks to understand mechanical hysteresis and functional fatigue, both of which are generally undesirable yet challenging to predict, model, and tune. As well, martensitic phase transformation is an incredibly complex mechanism that forms a hierarchical microstructure with mobile interfaces that both interact with and generate defects. As a result, understanding these phenomena pose a significant scientific challenge.
Employing a unique combination of advanced in-situ X-ray characterization techniques, Dr. Bucsek seeks to address several gaps in our scientific understanding of martensitic phase transformations: How does the propagation of interfaces contribute to mechanical behavior, and how can these contributions be quantitatively measured and modeled? How can we predict martensitic phase transformation mechanics, when local stress concentrations are present? How can we connect micromechanics and microstructure evolution to macroscopic mechanical behavior for martensitic phase transforming materials?
Dr. Bucsek’s proposal envisions a new comprehensive framework for understanding the mechanics of martensitic phase transforming materials. This framework will provide multiscale understanding of stress-activated martensitic phase transforming microstructures, will incorporate the importance of local microstructural defects, and will have broad implications for imperative crosscutting micromechanics challenges.
As well, Dr. Bucsek’s proposal includes an ambitious educational and outreach plan that combines her research with the methods and aligns with the goals of the U.S. Department of Education’s Strategy for STEM Education.
Firstly, to address comprehension difficulty of 3D mechanics concepts from 2D visualizations, Dr. Bucsek will partner with the University of Michigan’s Center for Academic Innovation. Together, this collaboration will create and develop interactive extended reality (XR) learning tools that will be used in undergraduate and graduate courses in combination with Dr. Bucsek’s research.
Secondly, Dr. Bucsek will partner with the University of Michigan’s Museum of Natural History to develop hands-on demonstrations that will connect physics concepts (such as diffraction, the spreading of waves around obstacles) to the measuring of physical, chemical, mechanical, and microstructural properties of materials. These will help to address the steep learning curve that has developed in the study of X-ray microscopy (the use of electromagnetic radiation for magnifying images of objects), caused by most students not being introduced to underlying physics concepts until college. As well, in collaboration with Engineering OnRamp, these learning tools will be presented at workshops brought directly to underrepresented K-12 students at a Detroit-based summer camp.
When asked how she feels about receiving this honor, Dr. Bucsek said, “Even more than the support provided by the award, it’s amazing to have the recognition of the NSF that the work that we do is valuable. It’s truly a career-changing affirmation that we’re headed in the right direction. Basically, it’s a big relief.”
Congratulations, Dr. Bucsek.