Influence of heat treatment on corrosion behavior of rare earth element Sc modified Al-Mg alloy processed by selective laser melting

Abstract In this study, electrochemical measurements, intergranular corrosion (IGC) resistance tests, X-ray photoelectron spectroscopy (XPS) and microstructure analyses were performed to study the influence of heat treatment on the corrosion behavior of SLM produced Al-Mg-Sc-Zr alloy. Electrochemical results and IGC tests revealed that the SLM-fabricated Al-Mg-Sc-Zr specimen possessed a superior corrosion resistance and a better IGC resistance than the heat-treated specimen. For both specimens, pitting was the main corrosion form and massive pits were formed along molten pool boundaries. Different corrosion morphologies were observed inside the molten pool for SLM-fabricated and heat-treated Al-Mg-Sc-Zr specimens after corrosion tests, where pits were generated along grain boundaries for the heat-treated specimen while no pits can be found inside the molten pool for the SLM-fabricated specimen. XRD and TEM analyses further revealed that the unfavorable corrosion resistance of the heat-treated specimen relates to the formation and coarsening of Al3(Sc,Zr) precipitations during heat treatment. The massive pits formed along molten pool boundaries were related to the refined grain size and aggregation of precipitations, and the different corrosion morphologies inside the molten pool were attributed to secondary Al3(Sc,Zr) precipitations generated at grain boundaries during aging process.