Abstract
Ni-29Mn-21.5Ga (at. %) wires are fabricated via a combination of (i) extrusion of liquid inks containing a binder, solvents, and elemental Ni, Mn, and Ga powders and (ii) heat treatments to remove the polymer binder and to interdiffuse and sinter the powders. To study the microstructural evolution, sintering mechanisms, and grain growth in these wires, both ex situ metallography and in situ X-Ray tomography were conducted while sintering at 800–1050 °C for up to 4 h. After debinding, Ga-rich regions melt and induce transient liquid phase sintering of the surrounding Ni and Mn powders, resulting in localized swelling of the wires and an increase in the wire porosity. After solidification of the melt and diffusion of the Ga into the Ni and Mn powders, solid-state sintering occurs. The interdiffusion of Ni, Mn, and Ga during solid-state sintering improves sintering compared to fully pre-alloyed powders. At the end of the 4 h sintering period, chemically homogenized, oligocrystalline wires with bamboo-like grains are observed with porosities ranging from 30 to 57%. Furthermore, significant grain growth occurs in wires sintered at 1000 and 1050 °C (11–35 μm vs. 1–10 μm initial powder size). The results from this study enable tailoring the porosity and grain size of printed Ni-Mn-Ga wires and 3D-printed micro-architectures and may be used to enhance their magnetic shape-memory and magnetocaloric effects in future work.
| Original language | English (US) |
|---|---|
| Pages (from-to) | 113-123 |
| Number of pages | 11 |
| Journal | Intermetallics |
| Volume | 104 |
| DOIs | |
| State | Published - Jan 2019 |
Funding
The authors acknowledge financial support from the National Science Foundation Grant No. 1207282 . SLT was funded by an NSF Graduate Research Fellowship . The X-Ray tomography was performed at beamline 2-BM at the Advanced Photon Source, a U.S. Department of Energy (DOE) Office of Science User Facility operated for the DOE Office of Science by Argonne National Laboratory under Contract No. DE-AC02-06CH11357. The authors gratefully acknowledge Dr. Xianghui Xiao and Mr. Pavel Shevchenko for help with the tomography setup and experiments at 2-BM; Mr. Ding Wen Chung, Mr. Fernando Reyes and Dr. Dinc Erdeniz (NU) for assistance with data collection during the tomography experiments; Dr. Eric C. Shiue (Biomilenia) for his assistance with writing python code for the data analysis. This work made use of the Materials Characterization Laboratory (MatCI), which received support from the MRSEC program (NSF DMR-1121262), and the EPIC facility of Northwestern University's NUANCE Center, which received support from the Soft and Hybrid Nanotechnology Experimental (SHyNE) Resource (NSF ECCS-1542205), the MRSEC program (NSF DMR-1121262) at the Materials Research Center, the International Institute for Nanotechnology (IIN), the Keck Foundation, and the State of Illinois, through the IIN. This work made use of the Materials Characterization Laboratory (MatCI), which received support from the MRSEC program ( NSF DMR-1121262 ), and the EPIC facility of Northwestern University’s NU ANCE Center , which received support from the Soft and Hybrid Nanotechnology Experimental (SHyNE) Resource ( NSF ECCS-1542205 ), the MRSEC program ( NSF DMR-1121262 ) at the Materials Research Center, the International Institute for Nanotechnology (IIN) , the Keck Foundation , and the State of Illinois , through the IIN .
Keywords
- Additive manufacturing
- Liquid phase sintering
- Magnetic shape memory alloy
- Porosity
- X-Ray tomography
ASJC Scopus subject areas
- General Chemistry
- Mechanics of Materials
- Mechanical Engineering
- Metals and Alloys
- Materials Chemistry
