THE PARTICLE-TO-MATRIX BOND IN DISPERSION-HARDENED AUSTENITIC AND FERRITIC IRON ALLOYS *

Abstract

The bonding strength, or ‘work of adhesion’, W, between particle and matrix in a number of austenitic and ferritic iron alloys has been determined from electron micrographs of the solid/solid contact angle, θ, at cavities formed by cold working and annealing. The critical strain to bring about cavitation, ε_c, was measured by plotting the strain corresponding to a sudden fall in rate of work-hardening. In deriving an equation to predict ε_c, account must be taken of the dependence of the equilibrium shape of the cavity on θ. Good correlation between experimental and predicted ε_c, as a function of W, was found. Brittle fracture of the matrix is likely to occur if θ is very low and the volume fraction is high. A criterion for brittle fracture, based on θ, is suggested which successfully predicts brittle fracture in one of the alloys studied.