Phase-Fraction Evolution During Incomplete Cyclic Transformation in TiNi: Correlation of Analytical Models with Magnetic Susceptibility Measurements

¹ Department of Materials Science and Mechanics, Michigan State University, East Lansing, Michigan 48824-1226, U.S.A.
² Department of Physics and Astronomy, Michigan State University, East Lansing, Michigan 48824-1226, U.S.A.

Abstract

The response of titanium-nickel, and other alloys exhibiting thermoelastic martensite transformations, display phase-coexistence and hysteresis over a wide range of temperature, arising from the fourfold splitting of a single transformation temperature into M_f, M_s, A_s, and A_f. Attempts to precisely characterize the evolution of phase-fraction during temperature reversals that involve incomplete transformation has led to the formulation of various hysteresis descriptions. We examine a description based on the Duhem-Madelung framework, which takes complete transformation behavior as constitutive input, and on this basis formally predicts the hysteresis associated with transformation arrest and reversal. In conjunction with this effort, a series of magnetic susceptibility measurements on TiNi has been conducted using a SQUID susceptometer. The measured hysteresis in the temperature/susceptibility curves are qualitatively described by the Duhem-Madelung model.