Microstructure and properties of Ni-Mn-Ga alloys produced by rapid solidification and pulsed electric current sintering

作者：Soderberg Outi^*; Brown David; Aaltio Ilkka; Oksanen Jussi; Syren Jesse; Pulkkinen Heikki; Hannula Simo Pekka

来源：Journal of Alloys and Compounds, 2011, 509(20): 5981-5987.

DOI：10.1016/j.jallcom.2011.02.166

• Intermetallics
• Rapid-solidification
• Sintering
• X-ray diffraction
• Magnetic measurements
• Mechanical properties

Ni-Mn-Ga alloys were compacted using pulsed electric current sintering (PECS) at 850-875 degrees C (50 MPa, 8 min) of flake-like powders made from the rapidly quenched melt-spun ribbons. Two kinds of ribbons were used: one made with a relatively slow wheel speed (6 m/s; average grain size similar to 14 mu m), and another with a faster wheel speed (23 m/s; average grain size similar to 5 mu m). Both sets of flake-like powders consisted of a mixture of non-modulated martensite (NM) and seven-layered modulated martensite (7M) structure. The amount of NM was greater in the slower speed material, while the other one exhibited mostly the 7M structure. These crystal structures were inherited by the sintered samples. In the compacts having the NM structure the multi-step martensitic reaction overlapped with the magnetic transition, and the Curie temperatures during heating and cooling differed from each other. In the compacts having mainly 7M structure the Curie point was about 100 degrees C and the martensitic transition took place in the paramagnetic state, while the intermartensitic one occurred in the region of 60-85 degrees C. This material demonstrated good magnetic properties and saturation magnetization, at best similar to 50 emu/g. Mechanical properties of the compacts were good, and comparable to those of the polycrystalline Ni-Mn-Ga samples in compression.

• 出版日期2011-5-19