A comparative study on corrosion and microstructure of direct metal laser sintered AlSi10Mg_200C and die cast A360.1 aluminum

Direct metal laser sintering (DMLS) is an additive manufacturing technique that creates near-net-shape functional components by selectively melting metal powders in two dimensions layer by layer using a high power laser as a heat source. This technique offers to create parts with complex net-shape structures at an affordable cost with the least lead time. The main purpose of this study is to investigate the corrosion behavior and microstructure of AlSi10Mg_200C manufactured using DMLS compared with its die cast counterpart (A360.1 die cast Al alloy). The impact of the alloy's surface finish, ie. as-printed surface versus as-ground one, on the corrosion performance was also investigated. Several AlSi10Mg_200C cube samples were additively manufactured through DMLS technique. In addition, the same size cubes were cut from an aluminum A360.1 die cast ingot. The corrosion behavior of the two alloys was analyzed utilizing potentiodynamic polarization testing and electrochemical impedance spectroscopy in aerated 3.5 wt.% NaCl solution to mimic sea water environment at 25 degrees C. Further, the microstructures and composition of the samples before and after corrosion testing were investigated using Optical Microscopy (OM), Scanning Electron Microscopy (SEM), and Energy Dispersive X-ray (EDX) spectroscopy. The results confirmed that the corrosion resistance of the alloy processed through DMLS was significantly better than the cast counterpart. This was attributed to the fine microstructure produced by DMLS, uniform distribution of the fine Si particles without formation of any intermetallic, due to the extremely rapid cooling and solidification rate during DMLS process and slightly lower Fe and Cu concentration of the AlSi10Mg alloy. In contrast, the A360.1 cast Al alloy samples experienced severe localized corrosion of the Al matrix in the periphery of the Fe containing IMC and Si flakes. The results also highlighted improved corrosion resistance of the as-printed DMLS sample compared with that of the as-ground one.