ABSTRACT
Early in the development of superalloys it became clear that the tensile properties of an alloy containing coherent precipitates of ordered γ' in a matrix of disordered γ could be better than those of either component alone. P. W. Davies and N. S. Stoloff compared the flow stresses of various nickel alloys at different temperatures. The chapter discusses the dependence of the yield stress on the size of the γ' particles are influenced by the orientation of the tensile axis. The most direct electron microscopical evidence of particle shearing appears when there is repeated slip on a single slip plane, and the shearing of particles across this plane is clearly visible. The next most direct evidence of particle shearing is the presence of stacking faults or antiphase boundaries (APBs) in the particles. If these are abundant after deformation, some particles must have been sheared by single dislocations, usually with Burgers vectors.
