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

Abstract

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. 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 compacts were able to be improved greatly by performing a solution treatment, and the tensile strength and elongation of the solution-treated compact became 570MPa and 6% respectively. The tensile properties of the solution-treated compacts were able to be improved fairly by performing the aging treatment, and the tensile strength and elongation of the aged compact became 750MPa 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 333K. The recovery stresses of the shape memory treated compact and the aged compact after loading of 2% pre-strain at the temperature change from 293K to 353K were around 250MPa. These shape memory treated compacts and aged compacts were well applicable to the shape memory functional elements due to their sufficient shape memory effect and good temperature-response.