Thermo-Mechanical Properties of Ti-Ni Shape Memory Alloy Fabricated by Spark-Plasma Sintering

摘要

The fabrication of Ti-Ni shape memory alloy by elemental powders was attempted by using a spark- plasma sintering method that can produce high-density sintered compacts in a very short sintering time. The relations between the fabrication conditions and the microstructures, tensile properties and thermo-mechanical properties of the sintered compacts were investigated systematically. The appropriate sintering temperature that can fabricate the sintered compacts whose relative densities are as high as about 96% was found. The tensile properties of the as-sintered compact were able to be improved greatly by performing a solution treatment, and the tensile strength and elongation of the solution treated compact became 570 MPa and 6% respectively. The tensile properties of the solution-treated compact were able to be improved fairly by performing the aging treatment, and the tensile strength and elongation of the aged compact became 750 MPa and 6.5% respectively. This result is one of the highest tensile properties that have been reported in powder metallurgy field so far. The solution-treated compacts showed a super-elastic like behavior above 333 K. The recovery stresses of the shape memory treated compact and the aged compact after loading of 2% pre-strain at the temperature change from 293 K to 353 K were around 250 MPa. These shape memory treated compacts and aged compacts were well applicable to the shape memory elements due to their sufficient shape memory effect and good temperature-response.