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The paper investigates the corrosion behavior of AlSi10Mg alloy produced by direct metal laser sintering (DMLS). Potentiodynamic tests were performed in aerated diluted Harrison solution, on specimens with different orientation with respect to the building plane. Different surface finishing were analyzed, covering rough surfaces as produced by DMLS and after polishing by means of emery papers and alumina slurry or chemical polishing with phosphoric and nitric acid bright dipping (BD). A conversion treatment by short immersion in Ce(III) salt solution was evaluated in order to improve corrosion resistance of both as-produced surface and polished surface. Selective attack of α-Al phase occurs at the border of the melting pools, typical of DMLS process, and slightly reduces on transversal planes, perpendicular to the building plane. Acid pickling slightly improves the corrosion resistance of as-produced surface, but no positive effects were noticed on polished one. The Ce(III) conversion treatment does not inhibit corrosion on as-produced specimens. Its effectiveness is higher on polished and pickled specimens. On polished surface, the effectiveness of conversion treatment mainly depends on plane orientation. [ABSTRACT FROM AUTHOR]

Abstract Laser powder bed fusion (LPBF) is one of the most widespread additive manufacturing (AM) technologies for metals, in which the components are built additively layer upon layer along the z-axis (the building direction) perpendicular to the building platform (xy-plane). Here, we evaluated the effect of post-processing heat treatments at 200, 300, and 400 °C on the corrosion resistance of AlSi10Mg alloy manufactured by LPBF for two orientations in the building chamber (XY – parallel to the building plane or XZ – perpendicular to the building plane). Electrochemical impedance spectroscopy (EIS) and potentiodynamic polarization tests were conducted at the constant chloride ion concentration of 0.02 M and 23 °C for the as-built and heat-treated specimens. All specimens were polished on the surface and displayed similar behaviors in the EIS tests. The pitting potential results were widely scattered and therefore analyzed using a statistical approach. Statistical data analysis based on analysis of variance technique (ANOVA) was performed. The results confirmed that the population significantly differs only by considering the heat treatments and the building direction plays only minor role. The cumulative distribution curves of pitting potentials showed a decrease in pitting resistance as the temperature of heat treatment increases. Graphical abstract Effect of heat treatment temperature on the pitting potentials of AlSi10Mg obtained by means of laser powder bed fusion. Image 1 Highlights • Pitting potentials of AlSi10Mg present a wide experimental variability. • Cumulative frequency of pitting potentials shows a deleterious effect of the temperature of post-processing heat treatment. • Corrosion attack take place at the edge of melt pool up to 300 °C of heat treatment temperature. [ABSTRACT FROM AUTHOR]

The paper deals with the effect of heat treatments on corrosion resistance of an AlSi10Mg alloy obtained by means of Direct Metal Laser Sintering. The tests were performed on as-processed alloy and after different post-heat treatment, covering stress relieving, annealing at high temperature and water quenching. Potentiodynamic and electrochemical impedance spectroscopy tests were carried out in aerated Harrison solution. The results show localized corrosion and selective penetrating attack at the border of melt pools on untreated or only stress relieved specimens. The selective attack was not observed after high temperature annealing. Modification of EIS plot evidenced galvanic coupling with silicon coarse particles that extensively precipitate during high temperature annealing. The morphology of precipitates is described in order to evidence their relevance in terms of rising selective penetrating attack and galvanic coupling. [ABSTRACT FROM AUTHOR]