Effects of magnetic frequency and the coupled magnetic-mechanical loading on a ferromagnetic shape memory alloy

Abstract

In the present work, the microstructure evolution and macro-response of a ferromagnetic shape memory alloy under stimuli of magnetic fields with different frequency and coupled magnetic-mechanical loading are investigated via a real-space phase field simulation. It is found that the coercive field is reduced from 0.724 to 0.423 with the magnetic frequency f decrease from 2.5 × 10 − 5 Hz to 0.833 × 10 − 5 Hz, wherein the concomitant domain wall motion and magnetization rotation are captured as well. Moreover, simulation results demonstrate that, under the coupled magnetic-mechanical loading, the coercive field of the magnetic hysteresis loop could be reduced by applying a compressive strain perpendicular to the magnetic field direction. The domain evolution is mainly divided into three types during the coupled magnetic-mechanical loading, namely (a) domain wall motion with the magnetization rotation, (b) pure magnetization rotation, and (c) 180° domain coordinated domain switching. To better understand the domain evolution, we propose an index S = m 1 avg + m 2 avg , with m 1 avg and m 2 avg indicating the absolute value of the averaged magnetization component m 1 and m 2 over the whole studied system, to characterize the magnetization change during the microstructure evolution.

A novel two-stage martensitic transformation induced by nanoscale concentration modulation in a TiNb-based shape memory alloy

“…Phase field models of spinodal decomposition and stress-induced MT are formulated based on a combination of Landau theory [20], gradient thermodynamics [21], and the modified Khachaturyan-Shatalov's microelasticity theory [22,23]. The concentration evolution during spinodal decomposition is governed by the Cahn-Hilliard equation [24], and the temporal and spatial evolution of the structural order parameters (which represent the parent and martensitic phases) during MT are described by the time-dependent Ginzburg-Landau equation [25][26][27][28]. The symmetry breaking accompanying the β (BCC, point group 𝑚3𝑚) → α (orthorhombic, point group mmm) MT [29,30] (see Fig.…”

Phase Field Simulations of Microstructures in Porous Ferromagnetic Shape Memory Alloy Ni2MnGa

“…The multi-phase-field model, as an effective physical-based computational approach, can simultaneously illustrate the evolution of ferromagnetic domain structure and martensite microstructure. In previous works, it has been widely used in the computer simulation of magnetic and mechanical properties of FSMAs [4,[21][22][23][24][25] with magnetoelastic coupling. The model is also able to predict the structures of porous materials [26,27].…”