Porous Titanium-nickel Alloys with Adjustable Porosity Fabricated Using Pore-forming Agent and Conventional Sintering

摘要

Porous nickel-titanium shape memory alloys (NiTi SMAs) with adjustable porosity were fabricated successfully by adding pore-forming agent ammonium bicarbonate and conventional sintering. It was found that the pore characteristics depended mainly on the shape and size of ammonium bicarbonate particles used, and the porosity of the alloys could.be tailored by controlling the amount of ammonium bicarbonate added. The porous NiTi SMAs fabricated mainly consisted of B2 and B19' NiTi phases, while less Ti2Ni, Ni3Ti and Ni4Ti3 phases were found even after a high temperature solution treatment. It was also found that the impurity phases increased in the porous alloys due to the addition of the pore-forming agent. In addition, a special 3-stage phase transformation took place in the porous NiTi SMAs, which was attributed to the inhomogeneity of compositions and phase constituents at grain boundaries. Moreover, phase transformation shows obvious influences on the damping behavior of the fabricated porous NiTi SMAs, while the influence from porosity was not obvious.