Comparison of martensite transformation temperatures in a NiMnGa alloy determined with hot/cold stage optical microscopy and differential scanning calorimetry

Calvin V. Hyatt; Shannon P. Farrell; Bob Armstrong; J. C. Bennett; Irv Keough; Gary Fisher; Jian Chen; Michael A. Gharghouri

doi:10.1117/12.484741

13 August 2003 Comparison of martensite transformation temperatures in a NiMnGa alloy determined with hot/cold stage optical microscopy and differential scanning calorimetry

Calvin V. Hyatt, Shannon P. Farrell, Bob Armstrong, J. C. Bennett, Irv Keough, Gary Fisher, Jian Chen, Michael A. Gharghouri

Author Affiliations +

Proceedings Volume 5053, Smart Structures and Materials 2003: Active Materials: Behavior and Mechanics; (2003) https://doi.org/10.1117/12.484741
Event: Smart Structures and Materials, 2003, San Diego, California, United States

Abstract

The martensite transformation temperatures of both as-grown and heat-treated specimens removed from a Bridgman grown boule of off-stoichiometric Ni2MnGa were determined by differential scanning calorimetry (DSC) and hot/cold stage microscopy. The work showed that martensite start and austenite finish transformation temperatures determined by the hot/cold stage microscope technique were in agreement with those determined by the DSC method. The hot/cold stage microscope technique was shown to be useful for characterizing variations of transformation temperature across a specimen. The results revealed that residual stress, deformation and boule composition variations produce artefacts in DSC traces which need to be identified, understood and controlled. Transmission electron microscope results suggest that the possible contribution of a premartensitic transformation to the high temperature edge of the martensite peak on DSC scans needs further investigation.

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Calvin V. Hyatt, Shannon P. Farrell, Bob Armstrong, J. C. Bennett, Irv Keough, Gary Fisher, Jian Chen, and Michael A. Gharghouri "Comparison of martensite transformation temperatures in a NiMnGa alloy determined with hot/cold stage optical microscopy and differential scanning calorimetry", Proc. SPIE 5053, Smart Structures and Materials 2003: Active Materials: Behavior and Mechanics, (13 August 2003); https://doi.org/10.1117/12.484741

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