The stress at which dislocations are generated at a particle-matrix interface

Abstract

When a hydrostatic pressure is applied to a metal containing particles or inclusions of different elastic constant, the local shear stresses which develop can be large enough to cause the interface between the particle and the metal matrix to emit dislocations. We have measured the pressure (from which we calculate the local shear stresses) at which dislocations are first generated at SiO₂ and Al₂O₃ particles in a copper matrix at room temperature. The critical pressure, and thus shear stress, depends on the particle size. The maximum shear stress at the particle surface was about G/100 for 2000 Å diameter particles, rising to G/40 for 1000 Å diameter particles, where G is the shear modulus of the metal matrix.