Intermittent dynamics in externally driven ferroelastics and strain glasses

Abstract

The interplay of elastic anisotropy and disorder dictates many of the properties of ferroic materials, specifically martensites. We use a phase field model for ferroelastic athermal materials to study their response to an increasing external stress that couples to the strain order parameter. We show that these systems evolve through avalanches, and study the avalanche-size distribution for ferroelastic systems (large anisotropy and/or small disorder) and for the strain glass (small anisotropy and/or large disorder) using various statistical analysis techniques including the maximum likelihood method. The model predicts that in the former case the distribution is subcritical or power-law (in agreement with experimental observations) whereas in the latter case it becomes supercritical. Our results are consistent with experiments on martensitic materials and we predict specific avalanche behavior that can be tested and used as an alternative means to characterize strain glasses.

Suppression of acoustic emission during superelastic tensile cycling of polycrystalline Ni50.4Ti49.6

“…For example, A ~ 2 for Ni-Ti [63,64], a value that is 7 times lower than those for Cu-based shape memory alloys [65][66][67], and 3-5 times lower than those for Ni-Mn-based shape memory alloys [68][69][70], for both of which only one soft deformation mode is available [shear and shuffle strains of basal {110} planes along <1-10> directions], and display strong AE activity when driving the transition mechanically (Supplementary Note 4 in [52] and Refs [34,43,44]) or thermally [57,71,72]. Our experimental observation of weak AE in mechanically cycled Ni-rich Ni-Ti polycrystalline alloys is consistent with recent phase-field models [73,74] that predict that martensitic transitions in alloys with low elastic anisotropy become smoother and take place via low-energy avalanches, which are challenging to detect using AE. On sustained mechanical cycling, the weak AE becomes even weaker due to accumulation of retained martensite, which favours the formation of strain-driven martensite and weakens the first-order character of the B2-B19' transition [31][32][33].…”

Elastocaloric effect with plateau-shape adiabatic temperature change in Ni–Co–Fe–Ga strain glass alloy

“…To deeply understand the eCE during the STG transition for the Ni 55−x Co x Fe 18 Ga 27 system, a phase field simulation was performed. For simplicity, a generic single crystal undergoing cubic-tetragonal martensitic transition was selected as the pure martensitic terminal in the phase field model, and the influence of defects on the martensitic transition was also considered to generate the STG [20,[33][34][35]. The three variants of tetragonal martensite were set as…”

Statistical analysis of emission, interaction and annihilation of phonons by kink motion in ferroelastic materials

“…2 The avalanche dynamics and the nature of the associated jerks determine the energies and amplitudes of avalanches and have been measured in many systems. 3,12,14,[22][23][24][25][26] The characteristic parameters like energy, amplitude, waiting time duration, and their correlations of jerks were found to be power law distributed. Their exponents are often linked to specific physical models like the mean field model, MF, or the "field integrated mean field model."…”