Materials Transactions, Vol.47 No.03 (2006) pp.607-611
© 2006 The Japan Institute of Metals
Acoustic Emission as a Probe of the Kinetics of the Martensitic Transformation in a Shape Memory Alloy
1Department of Materials Science and Engineering, Delft University of Technology, Rotterdamseweg 137, 2628 AL Delft, The Netherlands
2Netherlands Institute for Metals Research, Mekelweg 2, 2628 CD Delft, The Netherlands
3Department of Metallurgy and Materials Science, Ghent University, Technologiepark 903, B-9052 Zwijnaarde (Gent), Belgium
The kinetics of the martensitic transformation in a CuAlMn shape memory alloy (SMA) has been studied using the acoustic emission (AE) technique. It is demonstrated that the volume fraction of martensite as a function of time and temperature can be derived from the measured AE power. The fraction data obtained can be described by the Koistinen and Marburger (Acta Metall. 7 (1959) 59) equation with high accuracy, which indicates that the nucleation of martensite takes place heterogeneously and that the average volume of martensite crystals is constant over the extent of the transformation. The martensite-start temperature determined from the measured AE data is in good agreement with the value found by differential scanning calorimetry (DSC). Furthermore, the results of AE experiments on the SMA are compared with optical Confocal Laser Scanning Microscopy (CLSM) observations of the surface of the SMA. The observations show that both small and large martensite plates are formed both at the beginning and at the end of the transformation, which is in agreement with the assumption of a constant average volume of martensite crystals used in the Koistinen and Marburger model.
(Received 2005/8/30; Accepted 2005/11/7; Published 2006/3/15)
Keywords: acoustic emission, martensitic transformation, shape memory alloy, optical confocal laser scanning microscopy, differential scanning calorimetry
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© 2002 The Japan Institute of Metals
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