Local strains, calorimetry, and magnetoresistance in adaptive martensite transition in multiple nanostrips of Ni39+xMn50Sn11−x(x ≤ 2) alloys
Ni39+xMn50Sn11−x (x = 0.5, 1.0, 1.5 and 2) alloys comprise multiple martensite nanostrips of nanocrystallites when cast in small discs, for example, ~15 mm diameter and 8 mm width. A single martensite phase with a L10 tetragonal crystal structure at room temperature can be formed at a critical Sn co...
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| Format: | Article |
| Language: | English |
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Taylor & Francis Group
2013-01-01
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| Series: | Science and Technology of Advanced Materials |
| Online Access: | http://dx.doi.org/10.1088/1468-6996/14/1/015004 |
| _version_ | 1818937151718424576 |
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| author | A A Prasanna and Shanker Ram |
| author_facet | A A Prasanna and Shanker Ram |
| author_sort | A A Prasanna and Shanker Ram |
| collection | DOAJ |
| description | Ni39+xMn50Sn11−x (x = 0.5, 1.0, 1.5 and 2) alloys comprise multiple martensite nanostrips of nanocrystallites when cast in small discs, for example, ~15 mm diameter and 8 mm width. A single martensite phase with a L10 tetragonal crystal structure at room temperature can be formed at a critical Sn content of 9.0 at.% (x = 2), whereas an austenite cubic L21 phase turns up at smaller x ≤ 1.5. The decrease in the Sn content from x = 2 to 0.5 also results in a gradual increase in the crystallite size from 11 to 17 nm. Scanning electron microscopy images reveal arrays of regularly displaced multiple martensite strips (x ≥ 1.5) with an average thickness of 20 nm. As forced oscillators, these strips carry over the local strains, magnetic dipoles, and thermions simultaneously in a martensite–austenite (or reverse) phase transition. A net residual enthalpy change ΔHM↔A = −0.12 J g−1 arises in the process that lacks reversibility between the cooling and heating cycles. A large magnetoresistance of (–)26% at 10 T is observed together with a large entropy change of 11.8 mJ g−1 K−1, nearly twice the value ever reported in such alloys, in the isothermal magnetization at 311 K. The ΔHM↔A irreversibility accounts for a thermal hysteresis in the electrical resistivity. Strain induced in the martensite strips leads them to have a higher electrical resistivity than that of the higher-temperature austenite phase. A model considering time-dependent enthalpy relaxation explains the irreversibility features. |
| first_indexed | 2024-12-20T05:47:24Z |
| format | Article |
| id | doaj.art-201e5db233d84b1684aeac24e62a6baf |
| institution | Directory Open Access Journal |
| issn | 1468-6996 1878-5514 |
| language | English |
| last_indexed | 2024-12-20T05:47:24Z |
| publishDate | 2013-01-01 |
| publisher | Taylor & Francis Group |
| record_format | Article |
| series | Science and Technology of Advanced Materials |
| spelling | doaj.art-201e5db233d84b1684aeac24e62a6baf2022-12-21T19:51:16ZengTaylor & Francis GroupScience and Technology of Advanced Materials1468-69961878-55142013-01-01141015004Local strains, calorimetry, and magnetoresistance in adaptive martensite transition in multiple nanostrips of Ni39+xMn50Sn11−x(x ≤ 2) alloysA A Prasanna and Shanker RamNi39+xMn50Sn11−x (x = 0.5, 1.0, 1.5 and 2) alloys comprise multiple martensite nanostrips of nanocrystallites when cast in small discs, for example, ~15 mm diameter and 8 mm width. A single martensite phase with a L10 tetragonal crystal structure at room temperature can be formed at a critical Sn content of 9.0 at.% (x = 2), whereas an austenite cubic L21 phase turns up at smaller x ≤ 1.5. The decrease in the Sn content from x = 2 to 0.5 also results in a gradual increase in the crystallite size from 11 to 17 nm. Scanning electron microscopy images reveal arrays of regularly displaced multiple martensite strips (x ≥ 1.5) with an average thickness of 20 nm. As forced oscillators, these strips carry over the local strains, magnetic dipoles, and thermions simultaneously in a martensite–austenite (or reverse) phase transition. A net residual enthalpy change ΔHM↔A = −0.12 J g−1 arises in the process that lacks reversibility between the cooling and heating cycles. A large magnetoresistance of (–)26% at 10 T is observed together with a large entropy change of 11.8 mJ g−1 K−1, nearly twice the value ever reported in such alloys, in the isothermal magnetization at 311 K. The ΔHM↔A irreversibility accounts for a thermal hysteresis in the electrical resistivity. Strain induced in the martensite strips leads them to have a higher electrical resistivity than that of the higher-temperature austenite phase. A model considering time-dependent enthalpy relaxation explains the irreversibility features.http://dx.doi.org/10.1088/1468-6996/14/1/015004 |
| spellingShingle | A A Prasanna and Shanker Ram Local strains, calorimetry, and magnetoresistance in adaptive martensite transition in multiple nanostrips of Ni39+xMn50Sn11−x(x ≤ 2) alloys Science and Technology of Advanced Materials |
| title | Local strains, calorimetry, and magnetoresistance in adaptive martensite transition in multiple nanostrips of Ni39+xMn50Sn11−x(x ≤ 2) alloys |
| title_full | Local strains, calorimetry, and magnetoresistance in adaptive martensite transition in multiple nanostrips of Ni39+xMn50Sn11−x(x ≤ 2) alloys |
| title_fullStr | Local strains, calorimetry, and magnetoresistance in adaptive martensite transition in multiple nanostrips of Ni39+xMn50Sn11−x(x ≤ 2) alloys |
| title_full_unstemmed | Local strains, calorimetry, and magnetoresistance in adaptive martensite transition in multiple nanostrips of Ni39+xMn50Sn11−x(x ≤ 2) alloys |
| title_short | Local strains, calorimetry, and magnetoresistance in adaptive martensite transition in multiple nanostrips of Ni39+xMn50Sn11−x(x ≤ 2) alloys |
| title_sort | local strains calorimetry and magnetoresistance in adaptive martensite transition in multiple nanostrips of ni39 xmn50sn11 x x ≤ 2 alloys |
| url | http://dx.doi.org/10.1088/1468-6996/14/1/015004 |
| work_keys_str_mv | AT aaprasannaandshankerram localstrainscalorimetryandmagnetoresistanceinadaptivemartensitetransitioninmultiplenanostripsofni39xmn50sn11xx2alloys |