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

摘要

The response of titanium-nickel, and other alloys exhibiting thennoelastic martensite transformations, display phase-coexistence and hysteresis over a wide range of temperature, arising from the fourfold splitting of a single transformation temperature into Mf, M,, A,, and Af. 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.