Microstructure, Corrosion Resistance and Tensile Properties of Modified Al-0.7Mn Alloy

A modified alloy (Al-0.7Mn) was designed and fabricated with an increased Mn content up to 0.7wt.% and a controlled Fe content of 0.1wt.% and compared with the conventional Al3102 (Al-0.3Mn) alloy using the air-slip casting process. Both alloys were homogenized at 510°C for 10 hours and then air-cooled. The microstructure, corrosion resistance, and mechanical properties of these materials were investigated. In the modified Al-0.7Mn alloy, the Mn/Fe ratios were found to be higher in both the α-Al matrix and the intermetallic compound of Al6(Mn, Fe) compared to those of the Al3102 alloy. Additionally, the size and volume fraction of the Al6(Mn, Fe) phase were relatively larger and higher in the modified Al-0.7Mn alloy, while the grain size of the α-Al matrix was significantly smaller. The galvanic corrosion test results indicated that the corrosion potential (Ecorr) of the conventional Al3102 alloy was higher than that of the modified Al-0.7Mn alloy (Al-0.7Mn: -682.1mV, Al3102: -652.4mV). In contrast, the corrosion current (Icorr) and corrosion rate were measured to be 49.86 μA and 0.541 mm/year for the Al-0.7Mn alloy, and 53.91 μA and 0.585 mm/year for the Al3102 alloy, respectively. Thus, it was confirmed that the corrosion rate of the Al-0.7Mn alloy was slower compared to the conventional alloy, indicating better corrosion resistance. Room temperature tensile results showed that the tensile strengths of the modified and conventional alloys were 92.55 MPa and 78.39 MPa, respectively, demonstrating that the modified Al-0.7Mn alloy achieved higher strength without a significant decrease in ductility. This improvement is attributed to the higher Mn/Fe wt.% ratio in the Al6(Mn, Fe) phase of the modified Al-0.7Mn alloy, which can reduce the detrimental effect of Fe element and enhance the corrosion resistance. Additionally, the larger size and higher volume fraction of Al6(Mn, Fe) in the modified alloy, along with the smaller grain size, may contribute to the higher tensile strength. Based on these results, the corrosion mechanisms and deformation behavior of the modified Al-0.7Mn alloy were also discussed.