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

Abstract

The magnetic domain structures and martensite microstructures of porous Ni2MnGa Heusler alloys with various circle-shaped and ellipse-shaped pores were systematically studied by the phase field method. The magnetization curves and magnetic field-induced strains (MFIS) at the external field were determined. A mesoscopic mechanism was proposed for simulation to reveal the influence of the pores on the microstructures and the MFIS of porous magnetic shape memory alloy. The stress concentration effect and the recovery strain of the porous alloy are studied. The results indicate the MFIS value increases when ellipse-shaped pores elongate along the twin boundary. The effects of porosity and pore size on MFIS for porous Ni-Mn-Ga alloys with randomly distributed pores were also explored. The present study is of guiding significance for understanding the role played by pores on the MFIS and may provide a possible way to adjust the functional properties of ferromagnetic shape memory alloys.

Keywords

• ferromagnetic shape memory alloy
• magnetic field induced strain
• Ni₂MnGa
• porous alloy
• phase-field method