Shape recovery characteristics of NiTi foams fabricated by vacuum process using of slurry

Abstract

In order to fabricate the NiTi foams with porosity over 80%, the vacuum process using of slurry was applied. The mixture of Ni and Ti elemental powders was dipped into the solution of 7.5 mass% polyvinyl alcohol, and stirred to make slurry. The lightly compacted lumps of slurry were subjected to diminished atmospheric pressure to make foamed compacts. The green foams were debound and sintered in vacuum into NiTi sintered foams with 85% porosity. X-ray analysis showed alloying of NiTi was completed by the sintering at above 1100°C. X-ray diffraction analysis and DSC measurement also indicated that the NiTi foams consisted of B2 austenite and B19' martensite phases. From the measurement of shape recovery strain, NiTi foams obtained from this process showed the far excellent shape recovery characteristics compared with those of NiTi bulk materials.