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 to 0.065 eV due to the synchronous migration of elements Fe—Mn—Si. Specifically, as the elements 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.