Relationship between elements migration of α-AlFeMnSi phase and micro-galvanic corrosion sensitivity of Al-Zn-Mg alloy

First principles calculations and scanning Kelvin probe force microscopy (SKPFM) were used to investigate the effect of elements migration of α-AlFeMnSi phase on micro-galvanic corrosion behavior of Al-Zn-Mg alloy. The simulation results showed that the average work function difference between the α-AlFeMnSi phase and Al matrix decreased from 0.232 eV to 0.065 eV due to the synchronous migration of element Fe-Mn-Si. Specifically, as the element Fe-Si migration during the extrusion process, the average Volta potential difference detected by SKPFM between the α-AlFeMnSi phase and Al matrix dropped down to 432.383 mV from 648.370 mV. Thus, the elements migration reduced the micro-galvanic corrosion sensitivity of Al-Zn-Mg alloy. To reach the calculated low micro-galvanic tendency between α-AlFeMnSi phase and Al matrix, the diffusion of Mn should be promoted during extruding process.