Energy barriers and hysteresis in martensitic phase transformations

(joint work with R.D. James and Z.Y. Zhang)

Abstract

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 lambda(2) = 1, where lambda(2) is the middle eigenvalue of the transformation stretch matrix, for alloys with X = Pt, Pd, Au. In all cases there is a sharp drop in the graph of hysteresis vs. composition at the composition where; lambda(2) = 1. When the size of the hysteresis is replotted vs. lambda(2) 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.

Brief Bio

Awards

1992 Prize of the European Mathematical Society

1993 Max-Planck Research Prize (jointly with V. Šverák)

1999 Member of the Academy of Berlin-Brandenburg

1999 Collatz prize of CICIAM

2000 Leibniz prize

2002 Member of the Academy Leopoldina

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