AUGER-ELECTRON SPECTROSCOPY ON BOTH FRACTURE SURFACES OF AN (001) (011) ASYMMETRICAL GRAIN-BOUNDARY/

Studies of grain boundary segregation by Auger electron spectroscopy r equire in situ intergranular brittle fracture of the bicrystal. During the separation, the segregated species are distributed between both r evealed fracture surfaces. In general, this distribution can be differ ent. To illustrate such a distribution, the chemical composition of bo th matching fracture surfaces of a segregated (001)/(011) asymmetrical grain boundary was studied in a bicrystal of an Fe-Si alloy containin g traces of P and C. The temperature dependences of silicon, phosphoru s and carbon concentrations at both fracture surfaces show that there are clear differences of segregants content: The concentrations of pho sphorus and carbon are systematically higher at the (011) fracture sur face while the concentration of silicon is lower as compared to (001). These findings suggest an asymmetrical nature of solute binding posit ion in the core of the 45-degrees [100] (001)/(011) asymmetrical tilt grain boundary in a-iron.