Abstract
TiNi shape memory alloys, which are representative of functional materials, have been applied in various fields such as medical and aerospace. To expand the application of TiNi shape memory alloy, the authors fabricated a functionally-graded TiNi shape memory alloy with a stepwise change in Ni composition in the material. Since the functionally-graded TiNi shape memory alloy is fabricated by powder metallurgy, the composition ratio of Ni can be controlled accurately and near-net-shape processing will be achieved. However, in general, strength and ductility of a sintered material are low due to the poor density. Therefore, the authors attempted to produce a sintered compact with a high density by increasing the sintering temperature. In addition, differential scanning calorimetry and tensile tests were conducted on the prepared functionally-graded TiNi shape memory alloy to clarify the transformation and mechanical properties. This study shows that a higher sintering temperature is an effective means of improving the strength and ductility of the TiNi shape memory alloy by increasing their density.
