Corrosion Behaviour of Additively Manufactured Al-Si-Cu Alloy Processed by High Pressure Torsion (HPT)

Abstract

The corrosion behaviour of an Al-Si-Cu alloy has been investigated in the project. The samples were subjected to high pressure torsion (HPT) in order to explore the relation between HPT and corrosion resistance and strength of the material. In order to make comparisons, the HPT was carried out under 0.25, 0.5, 1, 5 and 10 turns at room temperature. Corrosion tests have also been carried out on the samples that have undergone HPT testing in order to evaluate their corrosion resistance. The samples were grouped into two groups: group 1 (1 hour corrosion) and group 2 (24 hours corrosion). The summary of Group 1 results from corrosion were as follows: the OCP showed that the 0.5 hpt sample is the best in terms of corrosion resistance, the EIS showed that the 5 hpt sample has shown the highest corrosion resistance and the PPC showed that the 0.5 hpt sample has shown the highest corrosion resistance. On the other hand, the summary of Group 2 results from corrosion were as follows: the OCP showed that the 0.5 hpt sample is the best in terms of corrosion resistance, the EIS showed that the 10 hpt sample has shown the highest corrosion resistance and the PPC showed that the 5 hpt sample has shown the highest corrosion resistance. From the chemical analysis (EDS results), it was found that the 0.5 hpt sample has shown the lowest amounts of O which means it has the lowest corrosion resistance. On the contrary, the EDS results revealed that the 1 and 10 hpt samples have shown the highest amounts of O which means they have the highest corrosion resistance. On another note, the hardness results have shown that the lowest hardness was recorded for the as-received sample whereas the highest hardness was for the 5 hpt sample. The Alicona results have shown that the 5 and 10 hpt samples have shown the lowest corrosion rate, i.e. best corrosion resistance. Moreover, the surface roughness of the oxide layer (from Alicona), after corrosion, showed that the roughness is highest for the as-received samples compared to significantly lower roughness levels for the HPT-processed samples.