An upper bound to the free energy of mixing by twin-compatible lamination for n-variant martensitic phase transformations

作者：Govindjee S; Hackl K^*; Heinen R

来源：Continuum Mechanics and Thermodynamics, 2007, 18(7-8): 443-453.

DOI：10.1007/s00161-006-0038-1

• shape memory alloys
• martensitic phase transformations
• relaxation
• quasiconvexification
• lamination

Modeling the energetic behavior of martensitic (phase transforming) materials usually leads to non quasiconvex energy formulations. For this reason, researchers often employ quasiconvex relaxation methods to improve the character of the formulation. Unfortunately, explicit expressions for the relaxed free energy density for multi-variant martensitic materials are typically not available. Thus, some researchers have employed a Reu beta-like convex lower bound, which neglects compatibility constraints, as an estimate on the free energy of mixing. To be confident with such a technique, one needs a measure of the quality of the lower bound. In this paper, we seek such a measure by comparing the Reu beta-like lower bound to an upper bound. The upper bound is constructed upon assumptions on the type of microstructures that form in such alloys. In particular, we consider lamination type microstructures which form by temperature- or stress-induced transformation in monoclinic and orthorhombic Copper-based alloys with cubic austenitic symmetry. Our results display a striking congruence of upper and lower bounds in the most relevant cases.

• 出版日期2007-2