Spatial characterization of the thermal-induced phase transformation throughout as-deposited additive manufactured NiTi bulk builds

Transformation temperatures in NiTi shape memory alloys fabricated by laser based directed energy deposition with substrate heating were measured via differential scanning calorimetry. Elementally blended Ni and Ti powders produced Ni-poor (Ti53.1Ni46.9 at.%) and Ni-rich (Ni52.4Ti47.6 at.%) builds. Build volumes approaching three times the largest to date were fabricated, and specimens were extracted at selected locations to spatially resolve temperatures. Measurements were equivalent throughout as-deposited builds, and the dependence on Ni concentration corresponded to observations for conventionally processed alloys.