Thermal and acoustic noises generated by austenite/martensite transformation in NiFeGaCo single crystals

• Published in: Journal of alloys and compounds Vol. 658; pp. 29 - 35
• Main Authors: Bolgár, M.K., Tóth, L.Z., Szabó, S., Gyöngyösi, Sz, Daróczi, L., Panchenko, E.Y., Chumlyakov, Y.I., Beke, D.L.
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 15.02.2016
• Subjects: Acoustic emission; Acoustic noise; Austenite; Exponents; Heating; Martensite; Martensitic transformations; NiFeGaCo; Shape memory; Statistical analysis; Transformations; Acoustic emission; Shape memory; NiFeGaCo; Martensitic transformations
• ISSN: 0925-8388; 1873-4669
• DOI: 10.1016/j.jallcom.2015.10.173

Jerky character of austenite/martensite transformation has been investigated in NiFeGaCo shape memory single crystalline samples simultaneously by Differential Scanning Calorimeter, DSC, and by Acoustic-Emission, AE. Statistical analysis of the noise signals resulted in the same energy exponents, ε, about 1.7 ± 0.1 for heating, as well as 2.0 ± 0.1 for cooling, from both acoustic emission and thermal signals at low cooling rates (dT/dt = 0.1 K/min). The exponents of peak amplitudes of AE signals are α = 2.5 ± 0.1 and 2.9 ± 0.1 for heating and cooling, respectively. The obtained exponents fulfill the scaling rule (α−1)/(ε−1) = z with z = 2. Optical observation of the transformation confirmed that it takes place by single interface motion, i.e. the jerky character is the result of the stop-and-go type motion of this interface. •Same critical exponents of energy distributions for thermal and acoustic noises.•The above noises were created by single interface motion.•Asymmetric acoustic noise: higher activity during heating than cooling.•The critical exponents of energy and amplitude reflect the above asymmetry.