Mary Lyn C. Lim

Effective Hydrogen Diffusion in Aluminum Alloy 5083-H131 as a Function of Orientation and Degree of Sensitization

The effective hydrogen diffusivity in aluminum alloy (AA)5083- H131 (UNS A95083) for various orientations and degrees of sensitization (DoS) was investigated using AA5083/Pd bilayer membranes. Sensitization produced β-phase (Al3Mg2) precipitates. A modified Devanathan-Stachurski permeation method was used with hydrogen charging by open-circuit exposure to 0.01 M sodium hydroxide (NaOH) and detection via Pd hydride formation. The measured hydrogen diffusivity (DH,eff) in the longitudinal (L) or short transverse (S) direction was almost independent of AA5083 foil thickness, indicating bulk diffusion control. DH,eff was not sensitive to the DoS, ranging from 2 mg/cm2 to 49 mg/cm2. The average room temperature diffusivities of hydrogen, DH,eff (25°C), for the initial H charging cycle of as-sensitized foils, were determined by the slope (Lcorr2/6 vs. t) method to be 8.5 (±1.4) × 10−11 cm2/s along the S direction and 1.4 (±0.2) × 10−10 cm2/s along the L direction, with a 95% confidence level. By averaging indiv...