Optimization of the fracture mechanical properties of additively manufactured EN AW-7075

Abstract Additive Manufacturing (AM) is a new innovative technique that allows the direct manufacturing of complex products based on their 3D data in a layer technology without tools like molds. In the meantime there are lots of materials available for AM, e.g. plastics or metals. They are used in several areas of application like aerospace, aircraft, medical technology and the automotive industry. In order to fulfil the high requirements of these industrial branches, high-quality products are expected. Selective Laser Melting (SLM) enables the production of finished parts, which can be mechanically and thermally stressed to a very high level. In aerospace, aircraft and automotive industry the lightweight design is of paramount importance. Consequently, in these industries materials with low density and high mechanical properties such as aluminum alloys are used. Therefore, high strength aluminum alloy EN AW-7075 powder, which was not previously used for AM, was produced by gas atomization and processed by SLM. Initially, several process parameters were varied in order to find the set of process parameters for the best possible result. With this set of parameters samples were produced to examine the fracture mechanical properties. To investigate the influence of the building direction regarding possible anisotropic behavior, specimens were manufactured with starting notches parallel as well as perpendicular to the building direction. For the fracture mechanical examination compact tension specimens, according to ASTM 647-08, were analyzed in order to achieve fatigue crack growth curves. To compare AM products with the conventionally manufactured aluminum alloy EN AW-7075 two different conditions (as-built and heat-treated) were examined.