SLM processing of elementally blended NiTi shape memory alloy

Abstract

Since selective laser melting (SLM) is a master forming technology, the material properties of the SLM components are defined during the manufacturing process. The idea is then to use SLM for micro metallurgy, which means that powders of different composition can easily be mixed to give a small amount of a desired alloy, which is useful if only small amounts of a special alloy are required. In this study, the binary shape memory alloy (SMA) Nitinol is processed accordingly. The entire process chain is analysed. The powder blending leads to a particle size distribution (PSD) with D10 = 15.57 µm and D90 = 48.24 µm, which is well processable. With the developed SLM process parameter set and the corresponding manufacturing strategy crack free components with relative densities ρrel > 98.6 % are produced. For these samples, the homogeneity of the alloy components after SLM processing as well as the phase change temperatures required for the shape memory effect (SME) are investigated in dependence on the processing parameters. The best-suited parameter set is further used for the manufacturing of specimens for compression tests, in which the presence of the SME is proven with a mean recoverable strain εpp = 0.884 % after 10 test cycles.