Methodology for efficiently establishing processing-structure-property relationships for additive-manufactured age-hardened alloys
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In Additive Manufacturing (AM) of Inconel 718 the main focus lies on the primary solidification occurring in the build. The next critical processing step for age-hardened alloys is the post-built heat treatment. Since diffusivity depends on the spatial distribution of the elements, the solution treatment and age parameter established for conventionally manufactured Inconel 718 components will likely not be optimal for Additive Manufactured components. This study specifically focuses on developing methods to rapidly establish the post-built heat treatment for age-hardened alloys. It will be showcased on Inconel 718 fabricated by Electron Beam Melting (EBM). The method incorporates as well as reveals challenges and considerations that go along with the unique processing route of AM. Based on a thorough literature review on Inconel 718, Processing-Structure-Property-Performance (PSPP) relations and Electron Beam Melting, a PSPP chart is outlined and used to detect further research goals. It is recognized that the work on systematically evaluating and improving the influence on mechanical properties is most efficiently conducted by utilizing post-processing parameter. After identifying promising post-processing parameter in solution treatment and aging, a material library is defined based on a selection of strain-rate jump tests which are found to be advantageous based on the demand of AM and efficiency considerations. An efficient test geometry enables evaluating strucutral and property features in the direct vicinity of each other. Design of Experiments has shown to be useful for establishing efficient test matrixes on post-built heat treatment parameter. Analyzing the data revealed major porosity concerns in the AM feedstock material which are found to detrimentally affect the material’s ductility.