Evaluation of an Electropolishing Solution for use with Ni2MnGa

Fabricating small and smart devices from multifunctional materials requires the controlled preparation of surfaces. The effect of using electro-polishing solutions to improve surface finish and remove defects present at the surface on shape memory alloys, such as Ni-Ti, have been thoroughly characterized in the scientific literature. In contrast, the effectiveness of only a small number of electro-polishing solutions on magnetic shape memory alloys, such as Ni ₂ MnGa, have been systematically evaluated. Thus, predicting the mass removal rate for Ni ₂ MnGa, given a set of polishing parameters, is often inaccurate, causing a deleterious effect on the precision of sample preparation. This study seeks to evaluate the performance of an electro-polishing solution composed of sulfuric and phosphoric acid by measuring the surface finish, mass removal rate and number of defects removed by varying the current density, bath chemistry and bath temperature. Understanding this relationship allows better surface finishes, less mechanical polishing, a lower number of surface defects, and the ability to predict the amount of material removed from a sample, thereby giving increased control over critical dimensions in Ni ₂ MnGa thin films, foam, wires, and generally small-scale samples.