Surface alloying of aluminum with molybdenum by high-current pulsed electron beam

Highlights: • The surface alloying by HCPEB was used in the pre-coated Mo film on Al matrix. • Mo element was dissolved into Al matrix to form a Mo-rich alloying layer. • The alloying layer was composed of Mo, Al and acicular or equiaxed Al₅Mo phases. • Various structure defects, Al₅Mo nano-particles and refinement of Al grains were formed. • The corrosion resistance was tremendously enhanced by HCPEB irradiation. The surface alloying of pre-coated molybdenum (Mo) film on aluminum (Al) substrate by high-current pulsed electron beam (HCPEB) was investigated. The microstructure and phase analysis were conducted by X-ray diffraction (XRD), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The results show that Mo particles were dissolved into Al matrix to form alloying layer, which was composed of Mo, Al and acicular or equiaxed Al₅Mo phases after surface alloying. Meanwhile, various structure defects such as dislocation loops, high-density dislocations and dislocation walls were observed in the alloying surface. The corrosion resistance was tested by using potentiodynamic polarization curves and electrochemical impedance spectra (EIS). Electrochemical results indicate that all the alloying samples had better corrosion resistance in 3.5 wt% NaCl solution compared to initial sample. The excellent corrosion resistance is mainly attributed to the combined effect of the structure defects and the addition of Mo element to form a more stable passive film.