STRESS AT WHICH DISLOCATIONS ARE GENERATED AT A PARTICLE-MATRIX INTERFACE

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. © 1969 Taylor & Francis Group, LLC.