Improvement of Fatigue Strength in Lightweight Selective Laser Melted Alloys by In-Situ and Ex-Situ Composition and Heat Treatment

Selective laser melting is a powder-bed-fusion process that is applied to different alloys. Thus, it is essential to study what are the different process variables that affect the static, quasi-static, and cyclic mechanical properties. In this contribution, two examples of alloys are introduced: AlSi (AlSi12, AlSil0Mg) and Ti-6Al-4V. The influence of controlled cooling and degassing mechanisms of residual gases is investigated by structural analysis in electron microscopy and X-ray computed tomography. Controlled cooling through platform heating or multi-exposure treatments increased the dendritic width in AlSi alloys and decomposed alpha prime in Ti-6Al-4V. The alteration was a cause for enhanced ductility and slowing of crack propagation. The cyclic deformation is tracked during mechanical testing and is simulated in FE software using a high-throughput methodology to calculate Woehler curves based on Fatemi-Socie damage parameters. The cyclic deformation simulation is in agreement with the experimental data and quantified cyclic damage using Fatemi-Socie parameters.