Composition dependence of martensitic transformation and crystal structure in Ni50Mn25Ga25-xCux Heusler alloys

• Published in: Intermetallics Vol. 109; pp. 157 - 161
• Main Authors: Brzoza, A., Wierzbicka-Miernik, A., Czeppe, T., Cesari, E., Szczerba, M.J.
• Format: Journal Article
• Language: English
• Published: Barking Elsevier Ltd 01-06-2019; Elsevier BV
• Subjects: A. shape-memory alloys; B. alloy design; C. heat treatment; Chemical composition; Copper; Crystal structure; D. martensitic structure; Dependence; Heat treating; Heat treatment; Heusler alloys; Hysteresis; Martensite; Martensitic transformations; Organic chemistry; Transformation temperature; Water quenching; B. alloy design; D. martensitic structure; C. heat treatment; A. shape-memory alloys
• ISSN: 0966-9795; 1879-0216
• DOI: 10.1016/j.intermet.2019.03.019

A detailed analysis of the influence of Cu addition on the martensitic transformation and the composition dependent transitions in Ni50-xMn25Ga25Cux Heusler alloys after two types of heat treatment was carried out. The chemical modification affected the martensitic transformation temperature, which increased from 202 to 691 K upon Cu addition. The chemical modification also affects the type of martensite structure, which changed from a ten-layered through a fourteen-layered and finally to a non-modulated crystal structure. At higher Cu content of ∼9 atomic percent precipitation of a second phase occurs enriched in Cu that disturbs the monotonic increase of the martensitic transformation temperature. It was also shown that water quenching at 1173 K affects the temperature and hysteresis of the martensitic transformation, as well as the chemical composition and temperature range of the 14 M → 2 M inter-martensitic transformation. Additionally, a narrow to wide transition of the martensitic transformation hysteresis was found to be independent of the applied heat treatments.
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•Cu addition changes the martensitic transformation type in Ni50Mn25Ga25-xCux alloys.•Water quenching stabilizes the 14 M martensite phase in Ni50Mn25Ga25-xCux alloys.•Transition from a narrow to wide hysteresis of martensitic transformation occurs.