Qualification of selective laser-melted Al alloys against fatigue damage by means of measurement and modeling techniques

Abstract

Abstract. Aluminum alloys processed through selective laser melting possess unique features of microstructure, defect morphology and mechanical properties. Constitution of fine cellular dendrites results from the high-cooling rate of the melt pool during the consolidation process. Investigation of the microstructure by scanning electron microscopy identifies supersaturation of Si particles as a secondary strengthening mechanism. On the contrary, platform heating that induces coarser microstructure leads to migration of Si particles from the Al matrix to the eutectic phase. As a result, tensile strength is reduced by 3%, while fracture strain is increased by 17%. Fine-grained structures exhibit a lower amount of plastic damage accumulation as well as delayed crack initiation as determined by the applied measurement techniques. Finite element models of the investigated configurations are obtained using scans of computed tomography under consideration of process-induced defects. Comparison of modeling and experimental results concluded that dominant fatigue damage mechanisms are related to the loading regime from low-cycle (LCF) to very-high-cycle fatigue (VHCF). Thus, process-inherent features of microstructure and porosity have different quantitative effects concerning the applied load. In VHCF, a material configuration with platform heating possesses an improved fatigue strength by 33% at 1E9 cycles, concerning the material configuration without platform heating.

Mechanical properties of additively manufactured AlSi10Mg under quasi‐static and cyclic loading

“…The reason is related to fine microstructure that resulted from high cooling rates during the LS process. 8 However, according to Bagherifard et al, the fatigue response of the LS-ed AlSi10Mg tends to be inferior to the conventionally fabricated AlSi10Mg. 9 The reason for this trend was clarified by the authors who cited the greater amount of porosities near the surface and the higher level of surface roughness found on the LS-ed component when compared to the conventionally produced one.…”