Hydrogen-accelerated spontaneous microcracking in high-strength aluminium alloys; Experimental and computational approaches

Tsuru, Tomohito   ; Yamaguchi, Masatake   ; Itakura, Mitsuhiro  ; Ebihara, Kenichi   ; Shimizu, Kazuyuki*; Bendo, A.*; Matsuda, Kenji*; Toda, Hiroyuki*

Highly concentrated precipitates generated by age hardening generally play a dominant role in shaping the mechanical properties of aluminium alloys. In such precipitates, it is commonly believed that the coherent interface between the matrix and precipitate does not contribute to crack initiation and embrittlement. We report an unexpected spontaneous fracture process associated with hydrogen embrittlement. The origin of this quasi-cleavage fracture involves hydrogen partitioning, which we comprehensively investigate through experiment, theory and first-principles calculations. Despite completely coherent interface, we show that the aluminium-precipitate interface is more preferable trap site than void, dislocation and grain boundary. The cohesivity of the interface deteriorates significantly with increasing occupancy, while hydrogen atoms are stably trapped up to an extremely high occupancy over the possible trap site.