An investigation was made of the mechanism via which segregated substitutional additions caused intergranular embrittlement. An electronic-level phenomenological theory was developed in order to predict the effect of a substitutional alloying addition upon the grain-boundary cohesion of metallic alloys. This was based upon first-principles full-potential linearized augmented plane-wave calculations of the strengthening and embrittling effects of Mo and Pd on Fe grain-boundary cohesion. Upon using the bulk properties of the substitutional alloying addition, A, and the matrix, M, as inputs, the strengthening or embrittling effect of A at a grain boundary of M could be predicted, without carrying out first-principles calculations, once the atomic structure of the corresponding clean grain boundary had been determined. Predictions were made of the embrittling power of a large number of metals, including 3d, 4d and 5d transition metals, with respect to Σ = 3 (111)Fe grain boundaries. Rigorous calculations of the effect of Co, Ru, W and Re upon the Σ = 3 (111)Fe grain boundary confirmed the predictions of the model. The latter was expected to be applicable to other high-angle boundaries.

Influence of Alloying Additions on Grain Boundary Cohesion of Transition Metals - First-Principles Determination and its Phenomenological Extension. W.T.Geng, A.J.Freeman, G.B.Olson: Physical Review B, 2001, 63[16], 165415 (9pp)