Size Scale Dependence of Deformation in NiTi

Recent work [1-5] has suggested that a lucrative future for shape memory materials such as NiTi is in the area of micro-electro-mechanical systems (MEMS). To design MEMS and predict their behavior during service, we must have quantitative information on the mechanical properties of scaled down NiTi materials. One way of obtaining the mechanical properties of scaled down materials is with unique MEMS testing fixtures. Although this approach is favorably analogous to macroscopic testing techniques it is not always feasible owing to the difficulty of handling the microscopic samples. Many smart material actuators are deposited thin films [1-5] and separating the films from their substrate and subsequently testing them is beyond our current MEMS processing and handling tools. An alternative method to quantify the properties of microscale materials is through micro-indentation, which has been previously applied to NiTi polycrystals [6]. Although micro-indentation is simple to accomplish, interpretation and quantification of the results is not as straightforward, as will be demonstrated in this work.