EFFECTS OF CATHODIC HYDROGEN CHARGING ON THE MECHANICAL-PROPERTIES OF AN AL-LI-CU-MG-ZR ALLOY

Mechanical properties of a commercial Al-Li-Cu-Mg-Zr alloy aged at 453 K were investigated with particular emphasis on the effects of cathodic hydrogen charging. Significant hydrogen permeation into the specimen was observed for the underaged conditions, and limited permeation for the coverage condition. This alloy showed a two-step hardening behavior on aging at 453 K, and the effects of hydrogen charging on the tensile properties were observed to differ for each steps. In the first step a slight strengthening was found, and in the second step a slight embrittling was seen. The Young's modulus, which was higher in the solution treated state than those of other high strength aluminum alloys, was gradually lowered by aging and also by hydrogen charging. The optimum balance in the mechanical properties under an influence of hydrogen is expected to be obtained at a slightly underaged condition.