A new way to obtain NiTi SMA superelastic meshes: investment casting followed by hot rolling

Abstract

In this work, NiTi superelastic meshes are manufactured through plasma melting followed by an injection into a mesh ceramic coating mold obtained by the lost wax technique. This is the first time such a manufacturing sequence is reported for NiTi SMA. Focus is given to the feasibility and efficiency of the manufacturing process. The as-cast NiTi meshes were afterward heat-treated and hot-rolled for thickness reduction and to increase malleability. After manufacturing, the meshes' thermomechanical properties were characterized. Differential scanning calorimetry showed that at room temperature the NiTi meshes can either be used as thermal actuators (using the shape memory effect) or as superelastic devices, depending on whether heating or cooling is performed prior to the application. This behavior leaves great potential for applications in engineering systems and biomedical uses. The superelastic behavior of the NiTi meshes was characterized through tensile tests at room temperature, showing very good cycling stability and strain recovering up to 4%. In the future, microstructural and biocompatibility investigations of the product will be evaluated to optimize the manufacturing process.

NiTi shape memory alloy cellular meshes: manufacturing by investment casting and characterization

“…In this work, NiTi SMA meshes are manufactured by investment casting. This technique has been recently used for the fabrication of near-net-shaped SMA parts with remarkable success [40,41]. Due to the poor machinability of NiTi SMAs [42], the complexity of obtaining NiTi metallurgical powders for powder metallurgy techniques [43] and the dimension limitation of laser cutting techniques due to the resulting heataffected zones [32,44], investment casting is very promising for obtaining NiTi SMA parts with small and complex shapes, satisfactory thermomechanical behaviour and relatively low manufacturing costs.…”

“…In this context, this work has two main objectives: first, to demonstrate the potential of the thermomechanical behaviour of NiTi SMA meshes, and second, to show the efficiency and versatility of investment casting to fabricate NiTi SMA meshes with different cell geometries [40]. This technique allows the fabrication of complex near-net-shaped parts in addition to having other advantages that are discussed herein.…”