Mechanical property and corrosion resistance of Al-Mg alloys Ni added by electron beam process

The changes in mechanical properties and corrosion resistance of Al-Mg alloys with the addition 10 mass%Ni by the electron beam welding process were investigated by the tensile test and the immersed corrosion test of the specimens with or without improved treatment in 1 x 10(-1) kmol.m(-3) HClO4 solution at 303 K. The X-ray diffraction or EDAX analysis of the precipitates and the observations of scanning electron micrographs of the specimens and the surfaces of the corroded specimens were also performed. The main results obtained are summarized as follows: (1) The needle structure of Al3Ni(beta) intermetallic compound and Al(alpha) + Al3Ni(beta) eutectic structure was precipitated by the improved treatment of Al-Mg alloys. Furthermore, the small size of teritectic structure of Al3Ni(beta) and Al3Ni2(gamma) intermetallic compounds was also detected. (2) The mechanical properties such as 0.2% proof stress and Vickers hardness of AI-Mg alloys were increased by the improved treatment. On the contrary, the values of U.T.S. and elongation of the improved specimens were reduced in comparison with the untreated specimens regardless of the AI-Mg alloys. (3) The corrosion resistance of the improved specimens decreased slightly compared with that of the unheated specimens. The deterioration of the corrosion resistance was caused by an electrochemical interaction of galvanic coupling produced between the grains of Al(alpha) phase in the eutectic structure and the Al3Ni(beta) intermetallic compound.