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Christopher A. Schuh. Payne, Madelyn (Madelyn I.) Massachusetts Institute of Technology. Department of Materials Science and Engineering. Massachusetts Institute of Technology. Department of Materials Science and Engineering 2021-10-08T18:28:37Z 2021-10-08T18:28:37Z 2019 2019 https://hdl.handle.net/1721.1/132913 1263579538 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, 2019 Cataloged from the official PDF version of thesis. Includes bibliographical references (pages 47-49). 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. by Madelyn Payne. S.B. S.B. Massachusetts Institute of Technology, Department of Materials Science and Engineering 49 pages eng Massachusetts Institute of Technology MIT theses may be protected by copyright. Please reuse MIT thesis content according to the MIT Libraries Permissions Policy, which is available through the URL provided. http://dspace.mit.edu/handle/1721.1/7582 Materials Science and Engineering. Exploring crystallographic compatibility in polycrystalline Cu-based shape-memory alloys Thesis application/pdf 2021-10-08T18:28:37Z Publication Bachelor MatSci unknown unknown <Publication xmlns="https://www.openaire.eu/cerif-profile/1.1/" id="35a0d8b9-e60a-416f-9861-0beedb854400"> <Type xmlns="https://www.openaire.eu/cerif-profile/vocab/COAR_Publication_Types">http://purl.org/coar/resource_type/c_1843</Type> <Language>eng</Language> <Title>Exploring crystallographic compatibility in polycrystalline Cu-based shape-memory alloys</Title> <PublishedIn> <Publication> </Publication> </PublishedIn> <PublicationDate>2019</PublicationDate> <Authors> <Author> <DisplayName>Payne, Madelyn (Madelyn I.)</DisplayName> <Affiliation> <OrgUnit> </OrgUnit> </Affiliation> </Author> </Authors> <Editors> </Editors> <Publishers> <Publisher> <DisplayName>Massachusetts Institute of Technology</DisplayName> <OrgUnit /> </Publisher> </Publishers> <License>http://dspace.mit.edu/handle/1721.1/7582</License> <Keyword>Materials Science and Engineering.</Keyword> <Abstract>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.</Abstract> <Access xmlns="http://purl.org/coar/access_right" > </Access> </Publication>