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NiMnGa Foams

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

Peiqi Zheng

The ferromagnetic shape memory alloy Ni-Mn-Ga show magnetically induced shape memory effect as well as the magnetocaloric effect[1] 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 [6]. Finally, we are investigating powder metallurgy methods to create Ni- Mn-Ga foams [7].

Related Publications
  1. 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)
  2. Boonyongmaneerat, Y., et al., "Increasing magnetoplasticity in polycrystalline Ni-Mn-Ga by reducing internal constraints through porosity", Physical Review Letters, 2007. 99(24).
  3. Chmielus, M., et al., "Giant magnetic-field-induced strains in polycrystalline Ni-Mn-Ga foams", Nature Materials, 2009. 8(11): p. 863-866.
  4. Cassie, Peiqi, et. al., "Size effect on polycrystalline Ni-Mn-Ga foams"(in progress).
  5. 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.
  6. Peiqi Zheng, Cassie Witherspoon, et. al. (in progress).
  7. 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


August 23, 2005