Ferromagnetic NiMnGa Shape Memory Alloy Foams
FIGURE 1: Polished cross-section of Ni-Mn-Ga foam with dual pores (black) within the Ni-Mn-Ga alloy (white). Chmielus et al., Nature Mat., 2009
The ferromagnetic shape memory alloy Ni-Mn-Ga show magnetically induced shape memory effect as well as the magnetocaloric effect and damping capacity, making it promising for use in actuators, magnetic cooling systems and energy-harvesting devices. Single crystalline Ni-Mn-Ga show giant magnetic-field-induced strain (MFIS: 10%) but are very difficult to process due to chemical segregation and evaporation during the growth process. Polycrystalline bulk Ni-Mn-Ga shows vanishingly small MFIS (~0.01%) due to incompatibilities between twins in neighboring grains. In collaboration with researchers at Boise State University (BSU), we showed that introducing pores in polycrystalline bulk Ni-Mn-Ga result into large (0.1-1%) to giant MFIS (1-9%) [2-3] by reducing constraints. The NU and BSU teams are investigating the effect of pore size and fraction in Ni-Mn-Ga foams [4-5]. We performed neutron diffraction on cast Ni-Mn-Ga foam sample (~1% MFIS) at Los Alamos National Lab to get a complete understanding of phase transformation and the twinning evolution during thermo-magneto changes . Finally, we are investigating powder metallurgy methods to create Ni- Mn-Ga foams .
- Carlo Paolo Sasso, Peiqi Zheng, Vittorio Basso, Peter Mullner, David C. Dunand, "Enhanced field induced martensitic phase transition and magnetocaloric effect in Ni55Mn20Ga25 metallic foams", Intermetallics, 2011(accepted)
- Boonyongmaneerat, Y., et al., "Increasing magnetoplasticity in polycrystalline Ni-Mn-Ga by reducing internal constraints through porosity", Physical Review Letters, 2007. 99(24).
- Chmielus, M., et al., "Giant magnetic-field-induced strains in polycrystalline Ni-Mn-Ga foams", Nature Materials, 2009. 8(11): p. 863-866.
- Cassie, Peiqi, et. al., "Size effect on polycrystalline Ni-Mn-Ga foams"(in progress).
- Effect of pore architecture on magnetic-field-induced strain in polycrystalline Ni-Mn-Ga, X. Zhang, C. Witherspoon, P. Mullner, D.C. Dunand, Acta Materialia 59 (2011) 2229-2239.
- Peiqi Zheng, Cassie Witherspoon, et. al. (in progress).
- Peiqi Zheng, Justin McMath, Uwe Gaitzsch, Peter Müllner, David C. Dunand, "Replication powder metallurgy of Ni-Mn-Ga foams" (in progress)
This Research is Funded by NSF