A new insight to regulate microstructure and enhance corrosion resistance of the Al-Mg-Si alloy by TCB seed alloy

This study proposed a new insight to design the microstructure, improve the corrosion processes and ameliorate the corrosion resistance of Al-Mg-Si alloy through TCB seed alloy. The studied alloys were devised with great resistance to pitting corrosion by achieving the AlMnFeSi phase with smaller size and disperse distribution, the finer grain structure as well as higher density and more evenly aging precipitates. Taking the 6061-1TCB sample immersed for 72 h in the 3.5 % NaCl aqueous solution as an example, the depth of corrosion pits decreases from 20 mu m to 4 mu m as well as the percentage of pitting corrosion decreases from 6.6 % to 2.1 % compared with the 6061 alloy. The great intergranular resistance can be obtained by the more tortuous grain boundaries and higher percentage of low angle grain boundaries. Taking the 6061-1TCB sample as an example, the deepest position of intergranular corrosion decreases from 728 mu m to 505 mu m as well as the area percentage of detached grains decreases from 65 % to 22 % compared with the 6061 alloy. Based on the enhancement of pitting and inter- granular corrosion resistance with TCB seed alloy, EXCO degree can also be improved from EA to PC level.