Quasi-static intergranular cracking in a Cu/1bSn alloy; an analog of stress relief cracking of steels

Part I: Anisotropy of cracking from oxygen-induced dynamic embrittlement in bicrystals of IN718

“…This behavior was also noted in the highly susceptible Cu-8%Sn alloy [4]. A later study of cracking of bicrystals of this alloy having symmetrical˙= 5 (013) tilt boundaries showed that it occurred much more rapidly along the tilt axis (i.e., the fast-diffusion direction) than perpendicular to the tilt axis [5].…”

“…* Corresponding author. The Cu-Sn alloy study involved the matrix element, tin, which is known to be surface active [4] and is an embrittling element in steels [6], for example. It has also been shown to segregate to grain boundaries in the Cu-Sn alloy during elevated-temperature aging [7].…”

Dynamic embrittlement–time-dependent brittle fracture

“…Examples are sulfur-induced cracking in alloy steels and tin-induced cracking in Cu-Sn alloys [2][3][4][5]. In both cases, the cracking appeared to initiate internally around cavities formed at intergranular inclusions during plastic flow, as illustrated schematically in Fig.…”

“…In this case, surface-segregated tin is the embrittling element [3]. Bicrystals having a symmetrical 5 [0 0 1] (0 3 1) tilt boundary were fabricated from this alloy by diffusion bonding of single crystals, and the cracking of the boundary was studied Fig.…”

Dynamic Embrittlement in Alloy 718

“…The interpretation of these crack surfaces is as follows: At the higher oxygen pressures the crack remained sharp and propagated in rapid jumps. Whereas in a Cu-Sn bicrystal the crack growth was continuous [17], it has been found to be discontinuous in all the cases of polycrystals studied so far [9,10,13,14]. This occurs because the rate of crack advance depends on the rate of diffusion of the embrittling element into the grain boundary ahead of the crack.…”