HYDROGEN EMBRITTLEMENT IN GRAIN BOUNDARIES STUDIED BY FATIGUE CRACK PROPAGATION IN Al-Zn-Mg BICRYSTALS A. NIEGEL, H.-J. GUDLADT et V. GEROLD J. Phys. Colloques, 49 C5 (1988) C5-659-C5-664 DOI: 10.1051/jphyscol:1988585