Corrosion characterisation of solid and lattice AlSi10Mg manufactured by laser powder bed fusion

Abstract

Additive manufacturing can be used to produce complex, custom geometries, consolidating different parts into one. This reduces the required number of assemblies and allows distributed manufacturing with short lead times. Defects, such as porosity and surface roughness, associated with parts manufactured by laser powder bed fusion, can severely limit industrial application. The effect these defects have on corrosion and hence long term structural integrity must also be taken into consideration. This project aimed to characterise porosity in both solid and lattice cube samples produced by laser powder bed fusion, with the differences in porosity induced by changes in the process parameters, and subsequently, characterising the effect porosity has on corrosion. The alloy used in this investigation is AlSi10Mg, which is widely used in the aerospace and automotive industries. Samples were studied before and after corrosion using X-Ray computed tomography (CT scanning), metallographic examination and scanning electron microscopy (SEM), as well as compression testing for the lattice cubes. It was found that higher laser power leads to more porosity and lower surface roughness. CT scanning was a very effective method to study corrosion using aligned CT images of before-after states. Porosity did not have an effect on the corrosion during the early corrosion stages (168 hours). The manufacturing process parameters induced differences in porosity and surface conditions, but did not strongly affect corrosion. It is probable that crack initiation sites such as internal porosity and defects are filled with corrosion product, delaying the onset of cracking and failure, and the corrosion product that fill the voids adding to the full strength of the lattice will also slightly increase the compressive strength of the samples.