Fracture in the Refractory Metals

Ab initiocalculations of grain boundaries in bcc metals

“…Our findings for R are in accordance with experiments [70], [72], [73], which show a preferred transgranular fracture for V, Nb, Ta, Cr and Fe, while Mo and W exhibit mainly intergranular fracture in the brittle fracture regime.…”

“…Further, all the metals not considered by DFT reveal rather large R values comparable with the ones obtained for Fe. Our findings for R are in accordance with experiments [4][5][6], which show a preferred transgranular fracture for V, Nb, Ta, Cr and Fe, while Mo and W exhibit mainly intergranular fracture in the brittle fracture regime.…”

“…is defined, where γ FS PCP denotes the surface energy of the preferred cleavage plane. For bcc metals, this is mainly the (1 0 0) plane [4,69]. If R is close to unity, transgranular cleavage is preferred, while for lower values intergranular fracture is expected.…”

“…The second goal of this investigation is to understand trends between the different bcc metals. Indeed, from experiments it is known that W and Mo have a tendency towards intergranular failure, while all other bcc transition metals prefer transgranular failure [4][5][6]. There has been a long debate whether this difference in failure mode is related to impurity segregation or whether it is intrinsic to the bonding of the clean metal [7][8][9].…”