Effect of directional solidification on texture and magnetic-field-induced strain in Ni–Mn–Ga foams with coarse grains

Abstract

Ferromagnetic Ni-Mn-Ga shape memory alloys with large magnetic field-induced strains are promising candidates for actuators. Here, we cast replicated Ni-Mn-Ga foams with 57 vol.% of 355-500 m open pores, with and without directional solidification. The 10M martensitic phase was determined in all foam samples. Directionally solidified foam had a fiber texture with <100> closely aligned with the solidification direction. In contrast, foams without directional solidification were more randomly textured. One directionally solidified foam showed a maximum magnetic-field induced strain of 0.65%, which was twice the value displayed by other foams without directional solidification. This improvement is consistent with a reduction in incompatibility stresses between neighboring grains deforming by twinning, generated by a reduction in crystallographic misorientation in textured foam.

Effect of process parameters on non-modulated Ni-Mn-Ga alloy manufactured using powder bed fusion

“…The highest reversible MFISs are found in single crystal structures, but these structures can be challenging to manufacture. In an effort to increase MFIS in polycrystalline structures, research has been made to both reduce constraints created by grain boundaries by manufacturing highly porous foams [15] or composite structures [16,17] with preferred orientation [18]. Manufacturing Ni-Mn-Ga foams requires the use of special casting replication techniques concomitant with directional solidification [18].…”

EBSD Study of the Influence of a High Magnetic Field on the Microstructure and Orientation of the Al-Si Eutectic During Directional Solidification

“…[23,24] The application of external fields has always acted as an effective method to modify the structures during the solidification process. [25][26][27][28][29] As we know, the application of a static magnetic field during the solidification process brings an unprecedented approach to realize the non-contact control of flows in the melt. [30][31][32] Normally, three extra forces in the liquid as well as the solid are introduced during solidification process.…”

Directional solidification and elastocaloric effect in a Ni45Mn44Sn11magnetic shape memory alloy

“…However, by the inclusion of the dual-phase structure, the entropy change and ΔT associated with MT decreased compared to the single-phase alloys. Alternatively, the texture formation in magnetic shape memory alloys provides a feasible way to improve their mechanical properties without scarifying functionality [26][27][28][29][30][31]. In order to obtain large ΔT and improve the mechanical properties, in this work, we prepared textured Ni-Mn-Sn polycrystalline alloys by a directional solidification method.…”