General Overview: Atomistics of Environmentally-Induced Fracture

Abstract

That the mechanical behavior of solids is affected by surface and environmental conditions is now well-known and was, in fact, the subject of an earlier NATO Advanced Study Institute on Surface Effects in Crystal Plasticity.1 While the plastics properties (yield strength, work hardening rate, etc.) are sometines substantially affected by the presence of surface films, solvent environments and the like, it is the remarkable effect of environments on the fracture of solids that is of most consequence in a technological sense. Generally the latter interactions are considered to be adverse, and this is often a reputation that is well deserved. Stress corrosion cracking2,3, hydrogen embrittlement 4,, liquid metal embrittlement5,6 and other such failure phenomena take on catastrophic consequences. As engineers, we are of course typically concerned with the prevention and or control of such failures. On the other hand, we should not forget that there are entire industries based upon the fragmentation of solids: materials removal operations such as metal cutting and ceramic machining, grinding, comminution, rapid excavation of hard rock, and others. Is it possible that in these circumstances one might use controlled embrittlement to advantage in order to reduce the work of fracture or fragmentation? While this approach is not typical of current practice in industry, it seems clear that controlled embrittlement is not only feasible but may well prove technologically attractive.