Analysis of liquid metal embrittlement from a bond energy viewpoint

Abstract

Absorption induced embrittlement of solid metals by certain liquid metals is analyzed through an Engel-Brewer calculation of the solid-liquid interaction energy, and the effect of the latter in reducing fracture surface energy. The reduction in fracture surface energy is estimated by comparison of the electronic contribution to the solid-liquid interaction energy with solid-solid bond energy for some 40 liquid-solid couples. Regular solution theory is used to estimate mutual solubility as the relative difference in parameter values. Embrittlement can be predicted by using reduction in fracture surface energy and solubility parameter difference as critical variables. The effect of solute additions to the liquid on the degree of embrittlement is interpreted via the same two variables; the principal effect of solutes is to modify solubility relationships at the solid-liquid interface. Finally, since solute additions to the solid may affect the yield stress, Petch slope and fracture surface energy in air, the Cottrell-Petch fracture relation is shown to be a necessary framework for interpreting the effects of such additions on embrittlement phenomena.