Observing strain glass transition in Ti33Nb15Zr25Hf25O2 high entropy alloy with Elinvar effect

Abstract

Exploring the phase transition of high entropy alloys (HEAs) with multiple major elements is of great importance for understanding the underlying physical mechanisms. Macroscopic martensitic phase transition has been frequently reported in HEAs, however, nanoscale microstructural phase evolution has not been investigated to the same extent. Herein, we have prepared the Ti33Nb15Zr25Hf25O2 HEA and investigated the strain glass transition and its associated properties using dynamic mechanical analysis and microstructure characterization. We have found that the elastic modulus in Ti33Nb15Zr25Hf25O2 HEA deviates from Wachtman's equation and observed the Elinvar effect in the form of temperature-independent modulus in the temperature range from 150 K to 450 K and frequency-dependence modulus around 220 K. The strain glass transition has been evidenced in Ti33Nb15Zr25Hf25O2 HEA by the formation and growth of nano-sized domains during in-situ transmission electron microscopy (TEM) cooling, and substantiated by the broken ergodicity during zero-field-cooling/field-cooling. The strain glass transition is believed to account for the Elinvar effect, where the modulus hardening of nano-sized domains compensates dynamically with the modulus softening of the transformable matrix.