The stress corrosion cracking(SCC) behaviour of 7A52 aluminum alloy in air and in 3.5% NaCl solution was researched by slow strain rate test(SSRT) and SEM-EDS. The SCC susceptibility was estimated with the loss of the reduction in area. The experimental results indicate that the SCC susceptibility of 7A52 aluminum alloy in 3.5% chloride solution is the highest at strain rate of 1×10-6 s-1. The lowest one is under the condition of 1×10-5 s-1. Stress concentration and anode dissolving around Al-Fe-Mn intermetallics initiate micropores which will result in microcracks. The existence of intermetallics in the microstructure may play an important role in understanding the SCC initiation mechanisms of 7A52 aluminum alloy.
Ni398 and Ni818 base alloy coatings were deposited on 1045 steel by electrospark deposition technique (ESD). Forming properties, thickness, microhardness and wear resistance of the coatings were investigated. The chemical composition and crosssection morphology were analyzed through energy dispersive spectrum (EDS) and metalloscope. The results show that the technological parameter window of Ni398 is larger than that of Ni818 electrode. However, other properties of the Ni818 coating, such as thickness and microhardness, were better than those of the Ni398 coating. Especially the wornout volume of Ni818 coating is only 1/6 of that for 1045 steel and 1/3 for Ni398 coating. Chemical composition analysis indicated that the addition of Mo promoted grain refinement of nickel alloy. Metallographic analysis shows that the molten droplets of Ni398 coatings have an average structure thickness of 20-40 μm while the microstructure of Ni818 coatings is flat with width of 5-20 μm.
