Cold spray additive manufacturing technology (CSAM) is a progressive method of 3D print of metals and alloys. Its inherent work principles allow production of the components below the material melting points, thereby avoiding several undesired material degradation processes. Among other inherently associated phenomena, the work principles of CSAM involve extreme plastic deformation of the materials, triggering formation of several types of lattice defects. Positron annihilation spectroscopy (PAS) is an analytical technique capable of studying deformation on the atomic scale level, even in extremely deformed materials. In our study, the first historical analysis of CSAM materials by PAS was carried out. For the demonstration, four different base metals were selected (Al, Cu, Ni, Ti). For these, the character of dislocations and vacancies was observed and the respective densities were quantified. The results show that the extremely high strain rate in the cold spray process prevents recovery of vacancies by diffusion to sinks. The deformation-induced vacancies agglomerate into small vacancy clusters. Hence, metals deposited using CSAM contain not only dislocations but also vacancy clusters. Both kinds of defects were detected by positron annihilation spectroscopy.

Cold spray (CS) is a progressive method for the deposition of metals and alloys whose principles involve considerable plastic deformation of the produced material at extreme strain rates. Positron annihilation spectroscopy (PAS) is an analytical technique capable of studying deformation on the atomic scale level, even in extremely deformed materials. In our study, the PAS method was used to characterize the deformation character at the lattice level and quantify the open-volume defects in four cold sprayed metals: Al, Cu, Ni, and Ti. As counterparts, bulk samples of these materials with ultrafine-grained structures were also produced by high-pressure torsion (HPT), a process exceeding cold spray in the total deformation, but having several orders of magnitude smaller strain rates, and by a traditional cold rolling process. The results show that the CS and HPT processes lead to the formation of similar lattice defects (dislocations and vacancy clusters), and both exhibit significantly higher dislocation densities than conventionally cold-rolled materials. Further, the vacancy clusters present in CS and HPT materials were not present in the rolled counterparts due to the lower vacancy production rate.