Corrosion Behavior of Arc Additively Manufactured AA 2319 Al Alloy under Different Heat Treatment Conditions
摘要
The heat treatment systems for additive manufactured components were investigated, and the determined heat treatment systems are as follows: T6 (538°C/5 h + 175°C/6 h), over-aging (538°C/5 h + 175°C/16 h), and RRA (538°C/5 h + 175°C/6 h + 260°C/30 min + 175°C/6 h). The corrosion behaviors of four types of samples, namely the as-deposited body, T6-treated, over-aged, and retrogression and re-aged samples, were compared. The results show that the as-deposited body has an inhomogeneous microstructure with a large number of second phases distributed at the grain boundaries, resulting in poor corrosion resistance. After T6 treatment, a large number of second phases precipitate within the grains, the microstructure uniformity is improved, and both the hardness and corrosion resistance are enhanced. After over-aging treatment, the second phases grow and aggregate, leading to improved corrosion resistance but decreased hardness. After RRA treatment, fewer second phases precipitate at the grain boundaries and they are in a discontinuous state, resulting in the best corrosion resistance, along with increased hardness, exhibits a hardness increase of 35.64 HV compared with the bulk counterpart. Further XPS results also indicate that the passivation film of the component after retrogression contains a higher content of Al2O3, thus exhibiting the best corrosion resistance.