Abstract
Selective laser melting process has already been developed for many metallic materials, including steel, aluminum, and titanium. The quasistatic properties of these materials have been found to be comparable or even better than their conventionally-manufactured counterparts; however, for their reliable applications in operational components, their fatigue behavior plays a critical role, which is dominated by several process-related features, like surface roughness, remnant porosity, microstructure, and residual stresses, which are controlled by the processing features, like imparted energy density to the material, its corresponding solidification behavior, the cooling rate in the process, as well as post-processing treatments. This study investigates the influence of these parameters on the cyclic deformation behavior of selective laser melted as well as hybrid-manufactured aluminum alloys. The corresponding microstructural features and porosity conditions are evaluated for developing correlations between the process conditions to microstructure, the deformation behavior, and the corresponding fatigue lives. From the numerical point of view, damage development with respect to process-induced cyclic deformation behavior is assessed by the phase-field method, which has been identified as an appropriate method for the determination of fatigue life at the respective applied stress levels. Fatigue strength of SLM-processed parts is found better than their cast counterparts, while hybridization has further increased fatigue strength. No effect of test frequency on the fatigue life could be established.
Highlights
Among different additive manufacturing (AM) techniques ranging from partial sintering to full melting, selective laser melting (SLM) process aims at the full melting of the powder material spread on the base platform by using a focused laser beam
This study aims at developing an extended profile of processing and post-processing aspects, and their corresponding part properties, like porosity, microstructure, and residual stresses for the selected Al-Si alloy
After post-process stress-relief, it is increased to 0.38%, which can be attributed to the extended duration of the applied temperature during the stress-relief procedure thatwould have developed an internal pressure in the pores, and a slight expansion of these pores would be possible resulting in a marginal expansion in porosity volume
Summary
Among different additive manufacturing (AM) techniques ranging from partial sintering to full melting, selective laser melting (SLM) process aims at the full melting of the powder material spread on the base platform by using a focused laser beam. The development side of the process can be considered at a mature stage such that it can result in almost fully-dense components, at least for some of the materials, like steel, aluminum, titanium, as well as some of the superalloys [1,2,3]. Imparted energy density is the dominant factor in determining the resulting part quality in terms of relative density; for the components to remain functionally stable under mechanical loading, these parameters have to be investigated carefully so that their influence on the part porosity, microstructure, as well as residual stresses can be considered in designing functionally reliable components.
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