{"id":{"repo_id":"mit","oai_identifier":"oai:dspace.mit.edu:1721.1/132913"},"canonical_url":"https://search.dev.ndltd.org/etd/mit/oai:dspace.mit.edu:1721.1/132913","repository":{"repo_id":"mit","name":"MIT","base_url":"https://dspace.mit.edu/oai/request"},"display":{"title":"Exploring crystallographic compatibility in polycrystalline Cu-based shape-memory alloys","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_html":"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_has_math":false,"creators":["Payne, Madelyn (Madelyn I.)"],"institution":"Massachusetts Institute of Technology","degree_name":"Bachelor","degree_level":null,"degree_discipline":null,"degree_department":"Massachusetts Institute of Technology. Department of Materials Science and Engineering","school":null,"contributors":[],"advisors":["Christopher A. Schuh."],"committee_chairs":[],"committee_members":[],"year":2019,"date_issued":"2019","date_published":"2019","updated_at":"2026-07-22T22:21:07Z","subjects":["Materials Science and Engineering."],"languages":["eng"],"rights":["MIT theses may be protected by copyright. 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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."]},{"key":"dc:description.degree","label":"Dc Description Degree","values":["S.B."]},{"key":"dc:title","label":"Title","values":["Exploring crystallographic compatibility in polycrystalline Cu-based shape-memory alloys"]}]}],"canonical_facts":{"dc:contributor.advisor":["Christopher A. Schuh."],"dc:contributor.department":["Massachusetts Institute of Technology. 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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. 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