Hydrogen damage and delayed fracture in bulk metallic glass

Abstract

Initiation, propagation, arresting and breaking of hydrogen blistering and hydrogen-induced delayed fracture (HIDF) under sustained load in a bulk metallic glass of Zr 41.2Ti 13.8Ni 10Cu 12.5Be 22.5 have been investigated. Results show that when the current density, i, is smaller than 20 mA/cm 2 corresponding to total hydrogen concentration of 3310 wppm, there are no hydrogen blistering and microcrack on the surface of the specimen without loading, but HIDF under sustained load can occur, and the threshold stress intensity factor for a single edge notched sample, K IH, is 0.63 times of the notched toughness, K Q, which is 62.2 MPa m 1/2. When i is equal to or larger than 20 mA/cm 2, hydrogen blistering or blistering plus microcrack appears on the surface of specimen without loading, as well as K IH is 0.26 times of K Q and independent upon i. The relative losses of the notched toughness induced by both atomic hydrogen and the blistering are all 37%. The critical pressure necessary for a stable blister formation, P i, is 3.6 GPa, and that for cracking of the blister, P C, is 3.9 GPa. The blister cracking will arrest after propagating for 20–30 μm, and the arrested crack will propagate again because of entering of hydrogen atoms. At last, the blister with cracking will break and leave local cleavage fracture surface with arrested lines on the sample surface without loading.