| Effects of cathodic hydrogen charging on fracture behavior of Al 8090 alloy were examined as functions of charging time, displacement rate, aging condition, applied potential and specimen orientations. Fatigue precracked SEN(single edge notch) specimens with various orientations were cathodically hydrogen charged in 0.1N HCl solution for 12 to 48 hours at an applied potential of -1800 and -2000mV vs. SCE, respectively. It was found that the cathodic hydrogen charging substantially reduced the initial fracture toughness value, K_(th), of Al 8090, while the reduction in K_(th) value was linearly proportional to (charging time)½. The dominant fracture mode of Al 8090 was intergranular dimpled rupture, and the plasticity around the dimples on the intergranular facets appeared to be reduced with hydrogen charging. The sensitivity to hydrogen assisted fracture of Al 8090 was greatly affected by specimen orientation, applied potential and aging condition. Like other high-strength Al alloys, the resistance to hydrogen assisted fracture was increased with increasing aging time. The reason for the improved resistance with prolonged aging in Al 8090 is believed to be related to the precipitate free zone formed along the grain boundaries. |
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