Selective laser melting (SLM) is a promising additive manufacturing process for fabricating complex geometries of metallic parts. The SLM processing parameters can have a major effect on microstructure and mechanical behavior of the fabricated metallic parts. In this work, the effect of laser spot size, hatch spacing, energy density, scan strategy, scanning speed and laser power on the microstructure and mechanical behavior of SLM-processed 316L stainless steel samples has been studied. These samples processed with different processing parameters were characterized by performing microhardness, tensile tests, x-ray diffraction (XRD) analysis, Energy dispersive spectroscopy (EDS) and scanning electron microscopy (SEM) analysis. The samples fabricated with a larger laser spot size exhibited higher tensile strength as well as higher microhardness values. A similar trend was observed for samples processed with higher laser power and hatch spacing. For the same energy density, higher laser power and lower scanning speed significantly enhance the mechanical properties of SLM processed samples compared to those fabricated with lower laser power and higher scanning speed. Therefore, it can be concluded that laser power has a more dominant role in governing the mechanical properties of SLM processed parts than scanning speed.
Nanocrystalline supersaturated Al-V alloys produced by high-energy ball milling have been reported to exhibit enhanced corrosion resistance and mechanical properties compared to commercial Al alloys. Corrosion of passive alloys such as Al-V alloy relies on the characteristics of the surface film, which is studied using scanning/transmission electron microscopy and time-of-flight secondary ion mass spectrometry. The effect of microstructure and composition on the surface film has been investigated after different immersion periods (30 min, 2 hours, and 1 day) in 0.1 M NaCl. The surface film was complex and composed of oxidized Al and V. The heterogeneous surface film was observed due to the presence of secondary phases and initiation of localized corrosion. The void formation was observed beneath the surface film that would potentially cause pitting corrosion. The generation of nano-sized voids was dependent on grain orientation. Compared to pure Al, the chloride penetration is suppressed in Al-V alloys. The effect of composition and microstructure on surface film formation and attendant corrosion behavior is discussed herein.
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