Abstract
The second-generation aluminum-magnesium-scandium (Al-Mg-Sc) alloy, which is often referred to as Scalmalloy®, has been developed as a high-strength aluminum alloy for selective laser melting (SLM). The high-cooling rates of melt pools during SLM establishes the thermodynamic conditions for a fine-grained crack-free aluminum structure saturated with fine precipitates of the ceramic phase Al3-Sc. The precipitation allows tensile and fatigue strength of Scalmalloy® to exceed those of AlSi10Mg by ~70%. Knowledge about properties of other additive manufacturing processes with slower cooling rates is currently not available. In this study, two batches of Scalmalloy® processed by SLM and laser metal deposition (LMD) are compared regarding microstructure-induced properties. Microstructural strengthening mechanisms behind enhanced strength and ductility are investigated by scanning electron microscopy (SEM). Fatigue damage mechanisms in low-cycle (LCF) to high-cycle fatigue (HCF) are a subject of study in a combined strategy of experimental and statistical modeling for calculation of Woehler curves in the respective regimes. Modeling efforts are supported by non-destructive defect characterization in an X-ray computed tomography (µ-CT) platform. The investigations show that Scalmalloy® specimens produced by LMD are prone to extensive porosity, contrary to SLM specimens, which is translated to ~30% lower fatigue strength.
Highlights
Metal additive manufacturing processes opened new dimensions of technological freedom through an extensive capability of tailoring property and function of metallic structures
This paper aims at the investigation of mechanical strength of Scalmalloy® in quasi-static and fatigue modes of loading such that a subsequent qualification to aerospace industry is possible
The current study aims to establish structure-property relationships for AlSi10Mg and Scalmalloy®
Summary
Metal additive manufacturing processes opened new dimensions of technological freedom through an extensive capability of tailoring property and function of metallic structures. Selective laser melting (SLM) and electron beam melting (EBM) are the flagships of this new technology. The two processes that have similar layout involve micro welding of powder layers with a thickness of. The primary advantage of the latter two over the more traditional selective laser sintering (SLS) is the complete melting of powder particles in micro melt pools. The total melting results in a melt track with higher structural integrity [2]. To this end, SLM and EBM technologies can be applied to manufacture structures subjected to dynamic loadings
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