Exploring crystallographic compatibility in polycrystalline Cu-based shape-memory alloys
Author(s)Payne, Madelyn (Madelyn I.)
Massachusetts Institute of Technology. Department of Materials Science and Engineering.
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Shape-memory alloys (SMAs) are a class of materials that can recover from apparent permanent strain (on the order of 5%) due to a solid-to-solid phase transformation. It has been recently suggested that SMAs satisfying a set of so-called cofactor conditions possess perfect interface compatibility and additional microstructural flexibility during transformation, which are theorized to result in excellent reversibility. Cu-based SMAs are cheaper than other alternatives, but polycrystalline Cu-based SMAs are unable to withstand many cycles because they are prone to cracking and degradation of functional properties. Previous research has identied improved shape-memory properties in Cu-Al-Ni-Mn SMAs in the oligocrystalline state, but polycrystalline material of the same composition has yet to be characterized. In this thesis, I characterize the compatibility of Cu-Al-Ni-Mn alloys according to the cofactor conditions and correlate these findings with results from superelastic mechanical cycling. Building on this knowledge, I also present a new alloy design that is predicted to meet the cofactor conditions and provides a promising path forward for a functionally stable, low-cost, polycrystalline Cu-based SMA.
This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections.Thesis: S.B., Massachusetts Institute of Technology, Department of Materials Science and Engineering, June, 2019Cataloged from the official PDF version of thesis.Includes bibliographical references (pages 47-49).
DepartmentMassachusetts Institute of Technology. Department of Materials Science and Engineering
Massachusetts Institute of Technology
Materials Science and Engineering.