Fabrication of Lotus-type Porous NiTi Shape Memory Alloys

摘要

NiTi alloys are widely used in industrial and medical devices because of their unique shape memory, superelastic effect, good corrosion resistance and biocompatibility. If the lotus-type porous NiTi can be, produced, it will be expected as a new category of light-weight shape memory alloys. In this work, lotus-type porous NiTi alloy whose long cylindrical pores are aligned in one direction was fabricated by continuous zone melting method in high-pressure mixture gas of hydrogen and helium. Under the partial pressure of hydrogen higher than 2.0MPa, the formed pores during solidification were rapidly combined and finally did not grow homogenously. Since the increase of pore volume by combination reduced the area of solid-liquid interface where supersaturated hydrogen was emitted from solid, enough hydrogen was not provided to the pores. However, lotus-type porous NiTi with elongated pores was successfully fabricated under the partial pressure of hydrogen lower than 1.75MPa.