Embrittlement of grain boundaries in Cu bicrystals induced by Bi segregation

Bi-doped Cu bicrystals with various [001] and [011] twist boundaries have been tensile tested at room temperature and 543 K. The fracture stress and fracture strain depend strongly on the misorientation angle and tensile temperature. The difference in the degree of embrittlement among different grain boundaries is more significant at 543 K. The fracture stress and fracture strain at 543 K against misorientation curves display some clear peaks; θ = 23°(Σ13A), 28°(Σ17A), 37°(Σ5) and 44°(Σ29A) for [001] boundaries and θ = 50°(Σ11), 59°(Σ33C), 71°(Σ3) and 83°(Σ57B) for [011] boundaries. For the two types of grain boundary, a good correlation is found between the degree of embrittlement and grain-boundary energy. A higher-energy boundary is more brittle and fractures more easily with a lower tensile stress. The fracture stresses of [001] boundaries are greater than those of [011] boundaries.