Collaborative Research – Enabling Magnetoplasticity in Polycrystalline Ni-Mn-Ga by Reducing Internal Constraints through Porosity Peter Müllner, Boise State University, David C. Dunand, Northwestern University, DMR Schematic of process to create (a) a foam, either by casting or powder metallurgy replication (depending on Step 1); (b) a tube by elemental diffusion Processing Motivation We aim to induce magnetoplasticity in fine-grained polycrystalline Ni-Mn-Ga, by introducing pores and textures in the material which reduce internal constraints during twinning of neighboring grains, and whose surfaces do not impede the motion of twinning dislocations, unlike grain boundaries. These foams or tubes will be used as magnetically-triggered actuators. Cross-section of cast replicated foams with (a) single pore size; (b) two pore sizes; (c) powder metallurgy replicated foam; (d) tube via Route III Magnetoplasticity Step 1: infiltrate space-holder with metal and solidify or Densify mixed metal and space-holder powders Step 2: dissolve all space-holder Step 3: dissolve some metal Step4: anneal Route I/II Sequential Mn/Ga and Ga/Mn interdiffusion Route III Simultaneous Mn and Ga interdiffusion Architecture and Microstructure a b c d Plot of magnetic field induced strain vs. temperature for directional solidified (DS) cast foam showing (a) the heating portions of four consecutive cycles; (b) the corresponding cooling portions. Correspon- ding plots for foam without DS showing (c) the heating portions of five consecutive cycles; (d) the corresponding cooling portions. (a) (b) Collaborative Research – Enabling Mangetoplasticity in Polycrystalline Ni-Mn-Ga by Reducing Internal Constraints through Porosity David C. Dunand, Northwestern University, DMR

Collaborative Research – Enabling Magnetoplasticity in Polycrystalline Ni-Mn-Ga by Reducing Internal Constraints through Porosity Peter Müllner, Boise State University, David C. Dunand, Northwestern University, DMR Broad Impact Our work has been presented in several conferences. Promising projects results have been published, or submitted, or is in draft. 1.Peiqi Zheng. Processing and Characterization of Ni-Mn-Ga Shape-Memory Fibers and Foams. (4/13). Ph.D. Thesis, Northwestern University. 2.D. C Dunand, P. Zheng, P. Müllner, P. Lindquist, B. Yuan (6/6/13). Fabricating Ni-Mn-Ga Microtubes by Diffusion of Mn and Ga into Ni Tubes. 4th International Conference on Ferromagnetic Shape Memory Alloys. Boise, ID. 3.Peiqi Zheng, Nikole J. Kucza, Peter Müllner, David C. Dunand (6/6/13). Enhanced Magnetic Field-induced Strain of Ni-Mn-Ga Foam by Directional Solidification. 4th International Conference on Ferromagnetic Shape Memory Alloys. Boise, ID. 4.P Zheng, P. Lindquist, B. Yuan, P. Müllner, DC Dunand (3/7/13). Fabricating Tubes of Ni-Mn-Ga Magnetic Shape Memory Alloys by Interdiffusion of Mn and Ga into Ni Tubing. TMS meeting. Antonio, TX. 5.Withherspoon, Cassie; Zheng, Peiqi; Chmielus, Markus; Vogel, Sven C.; Dunand, David C.; Müllner, Peter (4/13). Texture and training of magnetic shape memory foam. Acta Materialia. 61 (6), Zheng, P., N.J. Kucza, P. Müllner, and D.C. Dunand, Effect of Directional Solidification on Magnetic field-induced Strain in Ni- Mn-Ga Foams with Coarse Grains, submitted to Acta Materialia, Witherspoon, C., P. Zheng, M. Chmielu, D.C. Dunand, and P. Müllner, Effect of Porosity on the Magneto-mechanical Behavior of Polycrystalline Magnetic Shape Memory Foams. Submitted to Acta Materialia, Zheng, P., P. Lindquist, B. Yuan, P. Müllner, and D.C. Dunand, Fabricating Ni-Mn-Ga Microtubes by Diffusion of Mn and Ga into Ni Tubes. Submitted to Intermetallics, Zheng, P., N.J. Kucza, P. Müllner, and D.C. Dunand, Mechanical and magnetic behavior of oligocrystalline Ni- Mn-Ga microwires, in preparation. 11. Zheng, P., B. Ye, N.J. Kucza, P. Müllner, and D.C. Dunand, Oligocrystalline Ni-Mn-Ga Foams by Solid-State Replication with NaCl Spaceholders, in preparation. The American Physical Society and the National Science Foundation featured our foam results in Physical Revue Focus and on the NSF home page. Many docents of print and on-line media reported on these results including - Rosh-Gadol, an Israeli youth science magazine - Advanced Materials & Processes - Mobile Tex – Materials&Processes - Metall (Germany) - Materials Performance Education On April 26, 2012, Ms. Peiqi Zheng and four other female students from NU volunteered in “Take our Daughter and Sons to Work Day 2012” (a nationally recognized program which helps 8- to-16 year-old children focus on the numerous career options open to them). One female graduate student (Peiqi Zheng) finished her PhD at NU, and another two female graduate students (Ashley Ewh at NU and Nikole Kucza) at BSU) are working full time on the project. Collaborative Research – Enabling Mangetoplasticity in Polycrystalline Ni-Mn-Ga by Reducing Internal Constraints through Porosity David C. Dunand, Northwestern University, DMR