Abstract: NiTi shape memory alloys (SMAs) with different porosities were successfully fabricated by conventional sintering (CS) method with addition of pore-forming agent. Then damping capabilities of fabricated porous NiTi SMAs were characterized by measuring of internal friction (IF) using a dynamic mechanical analyzer (DMA). The internal friction (IF) value was found to have increased by 10% when the porosity decreased from 59% to 25%, which implies that the specific IF of the porous NiTi alloys is also influenced by the porosity. The results also showed that the IF value of the porous NiTi SMAs shows amplitude dependence in some specific amplitude regions when the strain amplitude of the measurement was changed in the range of 0.1 μm to 20μm, and the amplitude dependent region shifted and changed with the changing of sample porosity. This can be attributed to the different interactions between dislocations and other defects, as well as the influence of the pores inside the samples. Moreover, the relation between the thermal dynamic cycling and the IF behavior has also been investigated and will be discussed.

Keywords: Porous SMAs; strain amplitude; porosity; internal friction; dislocations; thermal dynamic cycling;