Fabrication of NiTi shape memory alloy hybrid composites for damping applications

Four set of three layered NiTi shape memory alloy (SMA) hybrid composites were fabricated using two compositionally different Ni50Ti50 and Ni51Ti49 SMAs. Diffusion bonding/spark plasma joining followed by hot roll bonding was utilized for fabricating monolithic hybrid SMA composites in two different configurations: equi-thickness and equi-strain partitioning. Microstructural characterization was carried out at every stage of joining, i.e. after diffusion bonding/spark plasma joining and after hot roll bonding to evaluate the integrity at the joining interface. DSC measurements were performed to determine the characteristic martensitic transformation temperatures of the base as well as NiTi SMA monolithic composites. Precipitation temperature regime was identified through DSC measurements and to arrive at the most suitable ageing heat treatment which can improve the pseudoelasticity in SMA composites. Finally, the damping capability of these SMA composites were evaluated through room temperature tensile tests. (author)