Embrittlement By The Localized Crack Environment

Papers included topics of phenomena, basic mechanisms, modeling, test methodologies, materials performance, engineering applications and service experience and failures and reflects the current emphasis with regard to material/environment systems.

The November 2000 symposium addressed methodologies for evaluation of environmental assisted cracking (EAC) in equipment and structures exposed to corrosive environments, and recent developments in the generation of relevant materials properties data based on laboratory tests. Twenty-seven papers fr

This invaluable reference provides a comprehensive overview of corrosion and environmental effects on metals, intermetallics, glossy metals, ceramics and composites of metals, and ceramics and polymer materials. It surveys numerous options for various applications involving environments and guidance in materials selection and substitution. Exploring a wide range of environments, including aqueous and high-temperature surroundings, Environmental Effects on Engineered Materials examines specific material-environmental interactions; corrosion rates and material limitations; preventive measurements against corrosion; utilization of older materials in recent applications; the use of new materials for existing equipment; and more.

For many years it has been recognized that engineering materials that are-tough and ductile can be rendered susceptible to premature fracture through their reaction with the environment. Over 100 years ago, Reynolds associated hydrogen with detrimental effects on the ductility of iron. The "season cracking" of brass has been a known problem for dec ades, but the mechanisms for this stress-corrosion process are only today being elucidated. In more recent times, the mechanical properties of most engineering materials have been shown to be adversely affected by hydrogen embrittlement or stress-corrosion cracking. Early studies of environmental effects on crack growth attempted to identify a unified theory to explain the crack growth behavior of groups of materials in a variety of environments. It is currently understood that there are numerous stress-corrosion processes some of which may be common to several materials, but that the crack growth behavior of a given material is dependent on microstructure, microchemistry, mechanics, surface chemistry, and solution chemistry. Although the mechanism by which various chemical species in the environment may cause cracks to propagate in some materials but not in others is very complex, the net result of all environmentally induced fracture is the reduction in the force and energy associated with the tensile or shear separation of atoms at the crack tip.

In order to predict when and how a material will crack under environmental conditions, engineers used to subject it to pressure for a long time, up to a year in cases; about 20 years ago, a testing method was developed that slowly but inexorably increases the pressure, which seems to cut down the ti