Energy barriers and hysteresis in martensitic phase transformations
Zhiyong Zhang, Richard D. James, and Stefan Müller
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Submission date: 04. Dec. 2008
published in: Acta materialia, 57 (2009) 15, p. 4332-4352
DOI number (of the published article): 10.1016/j.actamat.2009.05.034
Keywords and phrases: Martensitic phase transformation, hysteresis, nucleation and growth, nickel-titanium alloys, continuum mechanics
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We report results from a systematic program of alloy development in the system TiNiX, X = Cu, Pt, Pd, Au, to pursue certain special lattice parameters that have been identified previously with low hysteresis. We achieve , where is the middle eigenvalue of the transformation strain matrix, for alloys with X = Pt, Pd, Au. In all cases there is a sharp drop of the graph of hysteresis vs. composition at the composition where . When the size of the hysteresis is replotted vs. we obtain a universal graph for these alloys. Motivated by these experimental results, we present a new theory for the size of the hysteresis based on the growth from a small scale of fully developed austenite martensite needles. The energy of the transition layer plays a critical role in this theory. Overall, the results point to a simple systematic method of achieving low hysteresis and a high degree of reversibility in transforming materials.