Modified Phase-Field simulation of magnetoelastic domain in ferromagnetic shape memory alloys
Date Issued
2011
Date
2011
Author(s)
Chao, Chi-Pin
Abstract
Ferromagnetic shape memory alloys (FSMA) are those possessing both ferromagnetic and ferroelastic orderings. Their unique properties are due to the formation of very fine scale magnetic and elastic domains. As a result, these materials have been extensively studied by understanding how and why these domains are formed and arranged. One of the power tools for investigating them is to use the phase-field simulations.
Different from the “novel phase-field method” developed by the research group of Professor Shu, this thesis proposes a modification based on the new choice of phase-field variable [25]. It is shown that the modified method is more efficient and stable than the original approach. Second, we use this modified model, together with Landau-Lifshitz-Gilbert equation, to simulate the magnetoelastic couplings in FSMAs. First, the evolution equations are obtained by the vraiational argument and are solved numerically by Fast Fourier Transform (FFT). In Section 4.2.1, the simulated domain pattern is illustrated to agree well with the observed microstructure. Second in Section 4.2.3, it is shown that applied compressive stress can induce favorable magnetic domains. In addition, Section 4.2.4 demonstrates the effect of force and magnetic fields on the formation of magnetoelastic domains. It is found that magnetic-field-induced strain in FSMAs results from the process of variant rearrangement. Yet such rearrangement can be blocked by a relatively large compressive stress. Finally, it is demonstrated that FSMAs exhibit quasi-plastic or pseudo-elastic behavior depending on the strength of applied magnetic field.
Subjects
Ferromagnetic Shape Memory Alloys
Modified Novel Phase-Field Method
Microstructure
Type
thesis
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