Role of heat treatment and cathodic charging conditions on the hydrogen embrittlement of HP 7075 aluminum alloy

The response of an equiaxed-grained, high-purity 7075 aluminum alloy to hydrogen as a function of heat treatment and temperature of cathodic charging has been studied. Room-temperature (RT) tensile tests following RT or 120 °C cathodic charging revealed that hydrogen embrittlement susceptibility was dependent on both heat treatment and charging conditions. However, intergranular behavior was only observed following RT charging, limited to a zone a few grains deep from the surface. This fracture appearance has been considered in terms of the possible formation of an aluminum- or magnesium-base hydride at room temperature, compounds which are thermodynamically unstable at the 150 °C charging temperature. Reasons for the observed embrittlement following high-temperature charging are also considered.