Internal friction due to negative stiffness in the indium–thallium martensitic phase transformation

Abstract

Internal friction and dynamic shear modulus in an indium-21 at.% thallium alloy were measured as functions of frequency and cooling rate using broadband viscoelastic spectroscopy during the martensitic transformation which occurs in this material occurs around 50 C. Microstructural evolution of martensitic bands was captured using time-lapse optical microscopy. The amplitude of damping peaks due to the temperature-induced transformation in the polycrystalline alloy was found to exceed those reported by others for single crystals of similar alloy compositions, in contrast to the usual reduction in damping in polycrystals. The high temperature portion of the damping peak occurs before martensitic bands are observed; therefore this portion cannot be due to interfacial motion. Constrained negative stiffness of the grains can account for this damping, as well as for amplification of internal friction peaks in these polycrystals and for sigmoid-shaped anomalies in the shear modulus at high cooling rates. Surface features associated with a previously unreported pre-martensitic phenomenon are seen at temperatures above martensite-start.

Exploiting Microstructural Instabilities in Solids and Structures: From Metamaterials to Structural Transitions

“…[145] for a computational analysis showing damage and degradation surrounding the inclusion phase). Experiments on indium-thallium alloys showed damping peaks and sigmoid-shaped anomalies in the shear modulus at high cooling rates due to the temperature-induced martensitic transformation [152], which was also attributed to constrained negative stiffness. Further experiments were reported for BaZrO 3 -ZnO [153] and Zn 80 Al 20 -BaTiO 3 [154].…”

Viscoelastic, dielectric, and thermal properties of BaTiO3‐3%KNbO3

“…However, too fast a thermal rate would lead to a significant thermal gradient along the cross-section of the sample, which will reduce the apparent modulus softening during the transformation. Moreover, a high enough thermal rate would give rise to a sigmoidshaped anomaly in the modulus versus temperature curve in the vicinity of the transformation due to the effect of constrained negative stiffness elements by surrounding grains which have passed the transition temperature [14]. The transient term will vanish in an isothermal condition.…”

Broadband viscoelastic spectroscopy measurement of mechanical loss and modulus of polycrystalline BaTiO3 vs. temperature and frequency

“…The effect of constraint on negative stiffness elements by adjacent structures is considered here in the light of the following observations on indium-thallium alloy (InTl) [14]. In polycrystalline InTl, negative-stiffness elements constraint effects were inferred based on the fact that the mechanical loss in the polycrystalline material exceeded that for single crystals of similar alloy.…”