Abstract
Theoretical consideration is given to the initial yielding behaviour of directionally solidified, single-grained, binary eutectics under combined applied stresses. The eutectics are modelled such that one of the phases is in the form of aligned ellipsoidal inclusions embedded in a single-crystal matrix of the other phase. Homogeneous plastic deformation is assumed to be initiated in the matrix by means of crystallographic slip according to a Schmid-law criterion. By utilizing existing theories on related inclusion problems, a method for predicting the initial yield surface together with the active slip systems is developed and is applied to lamellar eutectics with particular reference to the Pb-Sn eutectic. Anisotropy of yielding behaviour, which depends strongly upon geometric and crystallographic orientation relationships between the phases, is illustrated by some numerical examples.